An intensely personal topic with specific answers for each individual.
For me, it is all about minimizing regrets. When you talk to people who know their time is soon at hand, they regret not having persued their youthful dreams. They wanted to play the violin, fly a plane, become a professional tennis player or any number of things.
They regret words they said and actions they did.
They regret not spending time with the people they wanted to, and regret not doing the things they simply wanted to do, but put them off as things to do 'later' when they had the time to do them.
No one says they regret not spending more time at a job they didn't love.