You are human and you are going to make mistakes, it's inevitable. You are going to do things that you will later come to think about and wonder why ever did that. It's hard to not regret things sometimes. You most likely will have moments where you will look back on your life and regret nearly everything. You will have moments of realization, and you will come to terms with all the decisions you have ever made. You will realize that in actually you have no regrets.
You may not be happy with the way certain things ended, you may not like the way you treated others in the past, you may rethink old conversations and wish you had just kept your mouth shut, or you might think back to an argument and cringe because you should have just kept your mouth shut. You will most likely go through a period where you just wish you could forget everything. You wish you could forget about all the people who hurt you, and vice versa. You wish you had made a better decision. You wish you hadn't been so naive or foolish in the past. You wish that you just never got the opportunity to meet certain people. You wish you could change the decisions you made. You wonder about how your life would have turned out if you could just go back and make the "right" decision. You wish you could have a do-over. It's hard not to regret things, it really is. But here is what you need to remember: it needed to happen this way.
You need to get hurt and sometimes as awful it is to say, you needed to hurt others along the way. You needed to make mistakes, and be young and dumb in order to get to where you are right now. Everything you have ever been through and everything you have every experienced has helped shape you. Whether you realize it or not, it has helped make you stronger and it has helped you come closer to the person you are destined to be. Every mistake you ever made, every tear you ever cried, every wrong turn you've ever made was all a part of the journey. All of it. You are who you are because of your mistakes. You need to mess up in order to find yourself. It all helps make you, you. It helps you grow into yourself. And if you think of it like that, how on earth can you regret any of it?