Hey try not to be too hard on yourself. You worried about the things that seemed important at that particular point in your life, this is no different. Life is just a series of phases and our priorities, concerns and worries change with each phase.
Try and recognise your accomplishments, that you are now better situated to address your current concerns and that you still have time to make a difference.
The past no longer exists, it did once, when it was present and happening, but it's gone now, it only exists in your mind as memories and thoughts and they have no power over you at all, you are the one responsible for your thoughts and consequently how you will feel in any given moment, as every emotion is preceded by a thought.
The future, which hasn't happened yet, but is unravelling with each passing second is what you hold in your hands, and you can mould it however you please, so make something good out of it.
Best of luck to you.