What I fear in a single sentence
From Kitchen Confidential (Anthony Bourdain):
My regrets will be more along the lines of a sad list of people hurt, people let down, assets wasted and advantages squandered.
Likewise, Time (Pink Floyd):
Tired of lying in the sunshine, staying home to watch the rain
You are young and life is long and there is time to kill today
And then one day you find ten years have got behind you
No one told you when to run, you missed the starting gun
Finally, Winston Churchill:
To each there comes in their lifetime a special moment when they are figuratively tapped on the shoulder and offered the chance to do a very special thing, unique to them and fitted to their talents. What a tragedy if that moment finds them unprepared or unqualified for that which could have been their finest hour.