I admit that I spend a lot of time thinking about "what might have been." But I don't spend much time regretting the past. in fact, the only meaningful regret I have in my life is not going to Ohio State and playing the Sousaphone in TBDBITL and dotting the "i". In other words, my life is pretty good!
But can you imagine being Pete Best? On the very cusp of success, you get kicked out of your band and replaced by a dorky looking, 2nd-rate drummer. OUCH!
Life is cruel. Read about it here (sorry about the long link - hope it works):