Gud, I struggle with beating myself up all the time over things that shouldn't cause me that much stress. I don't know if all the negative thoughts are coming from inside you or if some are from your wife so I'm not going to comment on your marriage.
You are a good person. A great person! You have all these wonderful qualities and the world is so much better and brighter with you here. Even when you make a mistake.
Here's what self care looks like for me (your mileage will vary): after I go to therapy currrently it means I take the long scenic way home through a mountain and where there are state parks and trails so if I need some fresh air or walk around and cry I can do that.
I carry a stuffed owl with me in my bag and when I get overwhelmed I pet it. At home it means petting my cat.
Sometimes self care for me is taking a nap or watching reruns of Chopped , coloring. Or killing zombies in a video game. Die zombies Die.
A therapist , a good therapist, can help you get perspective and also help change the way you think or help you learn new coping techniques. I used to misplace my keys all the time. It would go like - I'd misplace my keys, not realize until close to when I'd need to leave, I'd panic, "I'm terrible, horrible, irresponsible. I also do this becuase I'm a loser. I can't take care of anything" and maybe worse. While crying and panicking and freaking out.
So my therapist worked with me it started with stopping at the door when I got home and being aware of the keys in my hand "I'm holding my keys adn about to unlock the door." Then putting them in the same place and thinking "I'm putting my keys on the shelf." and tehn it became more or less a habit.
I still lose them but we also worked on me not beating myself up over misplacing the keys and reacting to it on an appropriate level.
That's what a therapist can do.