Look. I barely know Mick. Pretty much all I know about him is from fighting him. But he's your friend and he's been your friend for a long time. And that means something. He means something to you and to Lisa. No matter what else, you have to hold on to that.
I can't pretend I understand this. But I know you did the right thing, not killing him. You never should have been put in a position of feeling like you had to. If they locked him up in the ship once they realized he was this bounty hunter, they could have locked him up before, to let him cool down. It sounds like Rip was looking for the easy way out and made you feel like you didn't have another choice.
But you made the right choice, doing the right thing and saving your team. I know it had to be hard, but it was the right thing to do. You never meant to lose Mick. You said it yourself, you were going to go back for him. You just have to make him understand that. He's been hurt and he's been changed by the Time Masters, who sound like assholes by the way, and he probably doesn't believe that he can be better right now. But I have a lot of experience believing in people who don't believe in themselves. And you just have to keep believing and not give up.
You've been his friend as long as he's been yours. You can get through to him. If anyone can, it's you. And I know this has to be hard for you. But you'll get through this. I know you will. And I'll be here for you, no matter what. And so will Sara and Ray. You aren't alone in this. You'll get through to Mick. You'll save him. You just have to believe in yourself and in him. You have to believe that it's worth it.
And I know it might be hard, but maybe you should watch your show. See what made Mick turn on your team. Maybe if you understand why, you can figure out how to help him.
But maybe, right now, you need to take the same advice you gave me. Set it aside, just for a little bit, and focus on yourself. From the sound of it, you went through hell. And you're allowed to take the time you need to recover. Just let me know what you need, okay?