There's the secret. Self-reflection to assess what's lacking. Acknowledgement that you probably don't have the tools to fix your problems, so go to someone else to get those tools. This may mean therapy (not to cry on someone's shoulder for $$$/hr, but to learn techniques to deal with your shortcomings). And then work. Lots of work, probably for years. And finally, when you think of the terrible mistakes you made before (and they may only be terrible to you), remind yourself that you've dealt with or are dealing with the mistakes you made before and forgive yourself for those things.

And be prepared for the likelihood that this process may well go on for the rest of your life, even for big things. Wallowing in your past failings or escapism to avoid them doesn't solve the root problem, although a little escapism now and then can be a good break from the hard work of self-improvement.