This can go for NTs as well, it's not totally exclusive to Autism.
Ruminating over things that happened in the past, and all or nothing thinking.
Those two things steal joy from the present.
My husband ruminates over every indiscretion that has happened to him. From age 4 to now. It's all like insects in an amber mala prayer beads. He picks over each situation, relives it, gets into a huge funk that lasts for days. Some of it is he didn't understand the situation, and misread it totally. Also everything is weighted the same. The boy who shoved him in line in 1st grade is rehashed the same as that idiot boss who got him fired.
Also with my husband it is all you are right or you are wrong, except when it comes to him. Lol... People do crappy careless things. They don't think. It wasn't a calculated, I'm going to make you pay type thing. My husband sees everything that was bad or wrong done to him having this whole horrible back story to make his life a living hell.
So all that negative stuff taints the present. Yes, I have had horrible, sh***y things done to me. Some of it was people not thinking, and the unkindness and hurt came from that. People aren't perfect. People can be jerks. I am sure I have jackass things to people. I can't hold people to perfection, when I am nowhere near perfect. Then things that people do that are out right awful and cruel. Like the high school teacher that raped me twice. I could drag that toxic waste around in my head, but what good does it do? He was never prosecuted. Never held accountable. Every moment I think of that as*hole, it's stealing my present.
Life is short, and this maybe the only now I may get. I don't want the pass dragging down the good I have now. I wish my husband can give himself permission to release emotional part of it. You can forgive (let God, Karma, whatever sort it out, nothing I will think can change it), and not forget. I can remember the rape, but when I think about it, it doesn't have that emotional bondage over me anymore.
I've seen ruminating and rigid thinking steal more happiness from people than I can count.