I've tried to be flexible in my career by doing a little bit of everything and that's worked for me.
Forty is the line of demarcation that says you're an adult now. You're an adult, so don't pretend you're a kid anymore.
Ninety per cent of the world's woe comes from people not knowing themselves, their abilities, their frailties, and even their real virtues. Most of us go almost all the way through life as complete strangers to ourselves - so how can we know anyone else?