You absolutely do not have the best behind you! My bug "turnaround" came in the beginning of mt 50ies. Finally got to a stage in job life I like and also meet the woman of my life (after many years as single) and got married. I still feel that I haven't had the best yet when it come to job life and I plan to continue at least 20+ years working and have no plans of retirement. Today it make no sense at all to think about age, just keep up your motivation, drive and stay healthy and you can go on "forever". Find out what you really want to do and do it. There are no limits here in life