Sure, it's completely understandable and many of us had lots of anger and overwhelming emotions when we got sober. Keep reading here and you will find many posts about it.
I personally had to work through a lot of stuffed emotions, memories, old emotional wounds from my childhood and family, as well as newer anger and resentments ... it was kind of all rolled up into one big ugly ball. I got sober, and the ball began to unravel. So, yeah ... lots of stuff there to be dealt with.
We all deal with this in different ways though. There's therapy, AA, secular programs. Some of us have journaled our thoughts and feelings and got them out that way.
Exercise helps a little, as far as using up any extra anxiety. It will help regulate your sleep as well, and it's a mood booster. Many of us were depressed as well as anxious.
And there was the experience of all these old memories rising to the surface, people who'd said or done things that hurt me, and my gut instinct was to go really let them have it. I wanted to go back in time and relive that scene and do things differently -- maybe take up for myself, be more assertive, fend off the bullies, etc.
But we can't go back. We are here in the now. So, it's good that you find a way to deal with this anger in a healthy manner.
Revenge is never good. Doesn't accomplish anything except more hurt.
A life lived well, from here forward, IS something you can do.
Assertiveness should serve you well, btw. It's going to help you create healthy boundaries, better relationships, and yes, stand up for your rights. Good stuff.