Focus
Deciding what problems to work on, and saying no to many different things that are interesting to you.^[From Jony Ive interview where he says Steve Jobs would think about it: Saying no to things you really want to do, but instead choosing to focus on this one thing. https://www.youtube.com/watch?v=WSo_2tDETt4]
It is possible to lose many years to the wrong problems if they are not chosen carefully and intentionally.^[ Designing Your Life#^quote1]