Let go of your concerns about what you could have done or should have done. Look instead at your many opportunities for doing the right thing right now.
If your regrets about the past are painful, then allow those regrets to teach and to motivate you. In this moment you can take the valuable lessons you've learned and move forward with them.
You've learned that every action, as well as every failure to act, has consequences. Now is your chance to make those consequences work in your favor.
Though the past may indeed hold some regrets, you have something much more powerful. You have today.
And you have a future that will be shaped by what you do today. You can choose, right now, from a large set of valuable and desirable possibilities.
Based on your past experience, you are well qualified to be your own best advisor. Learn from what you've come through, and you'll find a way to go wherever you choose to go.