Wouldn't it be awful if old people took his advice. They'd be insufferable. It'd be a great argument for compulsory euthanaesia.
And what would be the point? Time isn't going to hand back the things it's taken. Resignation is the sensible option. Also prettier to look at. You need to know when to let go- but without losing interest. Not losing interest could be the trickiest part.
And sometimes, I'll admit it, the Dylan Thomas option does seem attractive.