The fact that you're questioning yourself is a good thing. It shows that you know you haven't reached your potential limit- which, for the record, I don't think exists.
All you have to do is learn from your past, Thor. Or, in this case, from another-you's past. Look at it, acknowledge the shortcomings and the mistakes made... and decide that you're going to be better in the future. That's all anyone can do, whether you're an average Midgardian or an Asgardian Prince. Be better tomorrow than you were today. That's what I mean by be better.
And if it comes down to it and you feel like this is the best you can do... you lean on your friends. Because I know that I am here for you, come Hell or high water. And I'm pretty sure other people feel the same way, like Captain Tight Pants and my new BFF Tony Stark. "The blood of the covenant is thicker than the water of the womb", and dammit, we got a pretty strong covenant going on here. If you stumble, we will catch you and help you get back on your feet, because that's what friends do. If you're in a self-hating spiral over things out of your control, we will love you and remind you that you're appreciated and valued, because that's what friends do.