Interesting mate, and what I'm about to say is not meant flippantly - we all make mistakes in life and we all create disappointments for ourselves.
As you very clearly realise it's how you deal with those disappointments that determine their effect.
You can't change the past, but your can shape the future (I'm not saying this is easy, but it can be done).
Wherever you are in life it's more important what you do today and tomorrow than what you did yesterday in terms of determining your future.
If you can draw a line on the past, and create a series of small, achievable steps to take. Once you've achieved those you can set more meaningful (and challenging) targets.
Good that you've opened up here though mate, that's a positive as others will confirm. Hope the above is useful. Good luck.