Between the choice of a boring 20 year old, a 20 year old who fucks up, and a psychopath 20 year old, I'd choose the one who fucks up and grows over the boring one, and the boring one who never changes over the psychopath (assuming I'm not their worried Mam.) At least a 20 year old who fucks up is pushing things a little and can develop. The boring ones are all the little snotty pencil pushers, probably wanting to be doctors (and will be) when they should be accountants.
If you stop fucking up, at any age, it stops your ability to grow. Obviously there's pushing the limits of things, which isn't on, but if you're not out there trying stuff and sometimes making an error you've one foot in the grave. Although that being said pensioners get away with mayhem. They've probably learned and appreciated there's a lot of fucking giggles in it. The way they be throwing elbows to get what they want, literally and figuratively, should be an inspiration.