First, let me clarify something: yes, I do appreciate the awful irony in scouring a new biography of Karl Marx for productivity tips, as I found myself doing the other day. That's how entrenched my false consciousness is. Looking to Marx for advice on becoming a more efficient worker is roughly as absurd as seeking advice on running a profitable business from Jesus (radical socialist) or on people skills from Genghis Khan (genocidal warlord). Which is to say that someone will probably write a self-help treatise along those lines soon, since they've already done so with Jesus and Genghis Khan. In the meantime, we have Jonathan Sperber's Karl Marx: A Nineteenth-Century Life, just published by Norton – which, as part of its attempt to portray Marx as a real human, lets us peer round the study door to watch him work. So do you want to know How To Be Productive And Creative, The Karl Marx Way? Are you sure? Because it's not pretty.

Recently, on my first trip to Australia, I finally tasted Vegemite. At the time, I didn't realise I was having a philosophically significant experience, but according to the American academic LA Paul, I was. She uses the example of Vegemite to illustrate something that seems obvious, but that's actually rather intriguing, about "phenomenal knowledge" – the knowledge of what it feels like to experience something. The intriguing point is this: you can obtain such knowledge only from experience. No matter how much information I might be given by others about what Vegemite tastes like, that information can never amount to experiencing the taste itself. By the way, Vegemite tastes a lot like Marmite. I know: major anticlimax.

Anyone born in the 70s to parents of an even slightly knit-your-own-muesli disposition must have encountered the horror of "non-competitive games". The intention was excellent – to show that vanquishing other people needn't be life's guiding value – but non-competitive games fall short in one crucial respect: they're no fun. (Sorry, Woodcraft Folk, but you know it's true.) Recently, by contrast, I played Gears Of War: Judgment on a friend's Xbox, performed atrociously and had a brilliant time.

You almost certainly know at least one infuriating person who is what I'll call, for want of a better term, a life-choice evangelist. As the label suggests, LCEs are driven by the anxious insistence that whatever major decisions they've made – to get married, to have or not have kids, to sacrifice fulfilling work for a higher salary, or vice versa – are best for everyone. If he's married, an LCE will seem unable to comprehend why anyone wouldn't choose to be; if she's single and you're not, she'll drop hints that you should envy her freedom. Contradict an LCE, by suggesting an alternative life path, and you'll witness a face flicker of confusion, as if you might not be speaking English. If you really know nobody like this, then I'm afraid it's probably you. One simple test: at a wedding reception, have you ever, with aggressive joviality, asked an unmarried couple when they're going to tie the knot? Thought so.

I've never visited Finland. Actually, I probably never should, since it's a place I love so much on paper – dazzling, snow-blanketed landscapes, best education in the world, first country to give full suffrage to women, home of the Moomins – that reality could only disappoint. Even the staunchest Finnophile, though, might be sceptical on encountering the Helsinki Bus Station Theory. First outlined in a 2004 graduation speech by Finnish-American photographer Arno Minkkinen, the theory claims, in short, that the secret to a creatively fulfilling career lies in understanding the operations of Helsinki's main bus station. It has circulated among photographers for years, but it deserves (pardon the pun) greater exposure. So I invite you to imagine the scene. It's a bus station like any big bus station – except, presumably, cleaner, and with environmentally-friendly buses driven by strikingly attractive blond(e)s.

Until recently, I owned a mobile phone so chunky and ridiculous that people had started to laugh at it – including, memorably, the staff at the shop where I'd originally bought it. (In their defence, I'd had it since 2007, which is the Mesolithic period in phone years.) But if there's one thing psychology has taught us, it's that buying shiny gadgets is a guaranteed path to fulfilment, so I'm now the proud owner of a Nexus 4, a sleek, blemish-free slab of glass, 9mm thick. Well, I say "proud owner". "Proud but with a background hum of anxiety" is more like it. Because it is, after all, a blemish-free slab of glass – which means I can never quite forget the risk of dropping or scratching it.

The narrator of Joseph O'Neill's 2008 novel Netherland, a banker who has lived in both London and New York, seems permanently torn between the two – not merely as places to live, but because they embody different approaches to life itself. In London, he observes, people older than 40 considered themselves "over the hill and entitled to an essentially retrospective idea of [life]", as if all the exciting stuff were behind them, whereas in New York "selfhood's hill always seemed to lie ahead, and to promise a glimpse of further, higher peaks". That makes New York sound more fun, but on closer inspection both are depressing. Would you rather feel your life is over, or that the real you remains out of reach? Maybe O'Neill's globe-hopping banker would have been happier in some less self-regarding world city: Brussels, say, where they have good beer and shellfish, and probably – I'm guessing here – less existential angst.

If, like me, you've recently purchased a mattress, you'll know it's an astoundingly tedious and soul-depleting process – rendered only slightly less awful by the fact that when you do finally collapse, exhausted by indecision, in the middle of the beds department, there are plenty of places to lie down. Long ago, maybe mattress-shopping was a simple choice between "firm" and "soft", but these days it's a thicket of dilemmas. Memory foam, wool, gel, fibre? Solid-slatted or sprung-slatted? Lumbar zoning? Perhaps a pillow-top? This complexity at first seems hard to explain. Sure, it's nice to have options, but why deliberately aggravate customers, delaying the moment of purchase with so many extra decisions? Aren't mattress-makers aware of one of the best-known truths of consumer psychology: that too much choice makes people miserable?

It's a fairly well-established fact, in political psychology, that leftwingers report lower levels of happiness than rightwingers. (This fact, you may have noticed, is self-reinforcing: learning of it makes leftwingers even gloomier.) What's much less clear is why. Conservatives like to argue that it's because the things they value – traditional families, faith, free markets – make people happiest. Liberals prefer to think conservatives are blinkered, clinging to an ideology that lets them avoid confronting life's grim truths; it's even been proposed that conservatism might be a mental illness. And there's an added complication: the social psychologists who study such questions, as the American academic Jonathan Haidt has complained, tend to lean left. But does that mean they are biased – or that, when you closely study the real world, you usually end up liberal? ("Reality has a well-known liberal bias" – Stephen Colbert.) It's all very murky – though if you're a liberal, like me, that's less of a problem, as studies suggest we might have more capacity for tolerating uncertainty. So there's that.

Earlier this year, two American bloggers triggered a global media convulsion by embarking on what they called a "mirror fast": covering the mirrors in their homes, and shunning mirrors elsewhere, in an effort to reduce what one of them called "the overriding self-consciousness that's taken up residence in my psyche". Since the social pressure to conform to ideals of beauty falls mainly on women, I can only guess what it's like to be so aware of one's appearance: I assume it's related to what I feel whenever a badly-angled photo reminds me how astoundingly bald I am. But for the fasters, the experiment proved a liberation. "All the other interests in my life – my goals, passions, friends, family, favourite hobbies, etc – have attracted the energy and attention I used to give to my looks," wrote Kjerstin Gruys, while Autumn Whitefield-Madrano said she felt "calmer and more serene". They'd pulled off an ingenious psychological trick. In a world obsessed with appearances, it's impractical just to decide you're going to think differently. What they'd done, instead, was to deny themselves the feedback that fuelled the fixation.