Lessons : Your past is behind you, live now.
Why do people (but not you) spend so much time looking back? What good does it do them? The future is nownownownownowNOW and is ever changing. Just think of how the world of work has changed and how if you plan to work in it you have to unlearn what you learnt and then learn what you need to in order to perform in this competitive environment.
People have nostalgia for the past, why not have nostalgia for the future?