Preface: This isn’t really about me but about a former co-worker (now friend) of mine.
After completing his apprenticeship in the company I’ve been working for, he was taken on as a full employee. He was and still is younger than 25, comes from a non-academic background, and won’t (can’t) go into any sort of academics himself. When he asked me for advice on his first tax return we talked about his budget - and he had little a concept of budgeting: it basically was “trying not to be below zero at the end of the month”. Though he was saving something in the 0.1% interest savings account with the cantonal bank, he no concept of investing either.
Though living quite frugal in many respects (though not by conscious choice rather than his hobbies and pastimes, and the fact that he lives with his family), the first thing he did after signing his contract with the company as a full employee was: leasing an expensive luxury car. We calculated that he spent about a quarter (25%) of his monthly take-home salary on the car alone (in leasing rates, registration, insurances, gas etc.) - and then some on enhancements and upgrades for it.
More out of wanting to prevent him from blowing all his money without saving, I convinced to him to open up a securities account a while ago. And then make regular ETF investments, through a savings plan.
He had had no idea about equity investments before and still isn’t much interested in the details of it, though he does keep tabs on his account every now and then. He’s still paying into four regular equity savings plans (three ETFs, one stock savings plan for a particular stock). Which I suggested, to get him into it: “Look, these is/contains companies whose products you like and use. Oh, and let’s also throw in an MSCI World fund to cover everything worldwide a bit” (the latter which I of course assigned the biggest allocation of his investments to).
Subsquently, he came back and asked me for advice a couple of times. Other than some technical advice on order types and setting limits, I gave him only very general advice (not panicking in downturns, taking it as a long-term endeavour, not chasing highs and lows, but that realising gains also doesn’t hurt…), though in the end left the ultimate decisions up to him.
Basically, he’s just starting out to save and invest for, while still being inexperienced and approaching investing pretty naively, without worrying about the details. Other than putting regular “savings” into it, he doesn’t “trade” frequently. Barely at all, in fact. Though he has made (just) a few conscious one-off transactions every couple of months - on his own, which surprised me, to be honest.
Now comes the maddening thing for me: so far, his portfolio performance has been wiping the floor with mine. 
Of course it’s no secret I’ve been holding off on making larger lump-sum investments due to the (perceived) high valuations.
But then, he’s also doing it by timing the market. 
As I said, he’s in no way trading frequently, has just made a handful select few one-off trades. And he hasn’t made them by looking at any ratios or PE growth figures or what not, let alone crunching number. He wouldn’t know how to anyway. He just logs the web banking to his portfolio every few days / weeks (?), and sold or bought when the price seemed “high” or “low” - or heading into the wrong direction - to him. On mere intuition, gut feeling… or luck? He doesn’t even follow economic or financial news and chatter at all, and stays totally unworried throughout.
The few of times he’s done this now, he’s done impressively well.
Taking the cake though…
We had a brief chat today, he showed me his portfolio data. And I noticed his (supposedly) biggest position in his World ETF was missing from his portfolio. I inquired, and he - literally - only vaguely remembered he had sold something earlier this year. I made him check, and he had in fact taken the biggest chunk out of his portfolio, and sold his World ETF on february 19 - at the historical all-time high bascially, give or take a week. For the simple reason that he had seen it had made “good” gains that he wanted to realise.
Needless to say, that is and will be hard to replicate. Yet my own take-away so far might be this: One shouldn’t overcomplicate things, overthink or crunch the numbers too vigorously. And not worry about thing. But still, trusting your intuition sometimes might prevent you from subsequent regret.
