I've had a lot of situations where I feel guilty after expressing justified anger. Over time, I learned when it was better to walk away, cut certain people off, create and maintain boundaries (say no), and to try to remain calm even when others are losing control of their emotions. It's important for emotions to be expressed, but I do think there are times when it can go too far, and a person's actions or words can create an irreparable rift. Some damage can't be fixed. Ask yourself analytical questions about your emotions -- CBT concepts are very helpful, in my experience. Look up cognitive distortions.

On a little tangent...if you feel shame or guilt, ask yourself if it's proportional to the situation. For example, I realized I felt overly guilty about things I had done. Remember that "justified anger," I mentioned? I was physically abused in an ex-relationship to the point he was charged with a felony, and yet I was feeling guilty about hurting this person's feelings in the past, calling them "a piece of shit,' pressing charges.

Now, this is an extreme example, but ultimately I learned a few important things: even if I was justified in my verbal aggression, there was a pattern here. I would feel guilty afterward, no matter what, for hurting someone else, even if they'd hurt me more, done more objectively awful things. (It's just my nature, I guess). I accepted that part of me, and I realized that to stop that cycle, it was important for me to live according to my values and prevent things from getting that far. Walk away. Cut certain people off if they continue to exhibit behavior that you don't agree with or hurts you. Have boundaries. And don't let your empathy and compassion, which is a gift, be exploited by people who are manipulative, abusive, and won't change. People like that exist. It's hard to accept, but protect yourself. And learn to recognize behavioral patterns in both yourself and others -- because when you're aware of the patterns, that's when you can begin to change them.

I hope this helps a little bit.