Advice based on hindsight is false wisdom
A friend of mine vividly recalls, during her last week at university, asking her favourite tutor what advice she'd give her younger self. The tutor had been a pioneering feminist historian, so my friend, not unreasonably, was expecting something sweeping and profound, born of decades of reflection. "Use moisturiser every day," was the answer she got. "And don't forget your neck." True, it wasn't particularly inspirational advice. But anyone can do inspirational advice. It's actionable advice that's truly rare.
There's a hefty sub-genre of self-help built around the question of what advice people would dispense if they could travel in time and meet themselves when younger: books such as What I Know Now: Letters To My Younger Self, and What I Wish I Knew When I Was 20, along with hundreds of online discussions in which older and wiser heads some of them, admittedly, apparently only about 22 themselves pass on the lessons of bitter experience. Some are amusingly specific ("Don't lose your virginity to Bryan") but the overwhelming majority is of the inspirational-but-empty variety: choose work you love; have more confidence in your abilities; stop worrying about insignificant stuff. A rare exception to the ruling blandness comes from the blogger Colin Marshall, who distils several such lists to their most pungent counsel. One genuinely valuable example: "Surround yourself with friends who don't care if you don't talk to them for three weeks at a stretch, but make sure you do talk to them more often than that."