By nature, I for years have chastised myself for missteps, misgivings and really anything that I later viewed as something that could have been taken the wrong way, that could have had the slight possibility of shedding a negative light on me or that just did not turn out how I wanted it to, no matter how small and insignificant. It took me pretty much until my adult life to convince myself that I am not the things that I do/have done. That they do not define who I am. Furthermore, there is no wrong decision once it's all said and done. Yes, you can choose a path that is more fortuitous to you -- one that will make you more successful, possibly more content, and that would leave fewer people hurt in the end. But once you are on that lower road... and you can't take any of it back, there is no benefit to despair or thoughts of "if I had done things differently..." At that moment, it is finished. It is sealed. At that moment, all you can do is know that you are exactly where you are meant to be, because there is no turning back. All you can do is be confident in that, listen to your discernment, and move forward. It will all be okay in the end. As long as you pursue what you are certain to be true and right, as long as you strive to fulfill your purpose and seek after the deepest desires of your heart, you will be on your right path.
And in all of this, you have to BE KIND TO YOURSELF. (I really struggled with this one. That is how the Mantra scarf was born). Don't torture yourself over things you can't change. Show yourself some grace. This is not to say that we should not take responsibility for our actions; I am merely stating that dwelling on them does no good for anyone. Do what you can to make it right, then forgive yourself and move on.
There is no need for regret. It is a poison that spoils talent, potential, passions and fulfillment. Your possibilities are limitless. GO.