How do you forgive?

It seems impossible to me. Is it a process? How is it done? I don’t really stay mad, but when my trust is lost I feel like it is literally impossible to get it back.

My husband has slowly over time lost my trust and I genuinely want to forgive him and move on. He made a mistake that was not a deal breaker for me, but it hurt me… and I don’t know how I can ever trust him again. I want to, but I don’t know how to do it. I love him and I want to get through this, but I feel like I am hindering our relationship because I don’t trust him, so it seems impossible to move forward and I am just constantly in a bad mood because I’m so stressed from all of this.