AnnaCia, there can only be 'failure' and 'success' when we have fixed ideas of how things 'should' be, when we insist on labelling, judging and comparing. All three (in quotes) are illusions.
While in the truest sense I have had neither failure nor success, in moments of giving in to the illusion it is easy to feel regrets. Regrets of course are not useful on the path of conscious evolution. Still I would entertain thoughts of how I would do things differently based on the learning, the evolution that has taken place.
As a seeker of truth and God from an early age, I kept saying, "let me know the truth, whatever it takes, however difficult it may be to accept." That banged me around a few corners but the growth in authenticity was worth the price.
Some things I would do differently (which is what I have learned) is gain emotional maturity - thereby reducing my dependence on others for my sense of well-being - and take on more self-responsibility earlier in life, be more sensitive and empathetic towards others, recognize my own authority rather than put authority outside myself, and stay more constantly in my center through whatever comes.