Cruel without meaning to be

My wife of ten years left me, and I felt completely blindsided. She said I'd been cruel for years (irritable, quick to snap over small things, unwilling to compromise; no yelling or name calling) and I kept defending myself by saying I was sorry I'd hurt her, yet I hadn't meant to do so. She came back to our space to pack up her things and we got into a short, awful fight that was entirely my fault, and I saw myself clearly. She's been right this whole time and I should've sought therapy years ago.

This relationship is irreparable (I've apologized and am giving her space as we finalize moving out and filing divorce), but I don't ever want to hurt someone like this again. I'm starting individual therapy + an autism assessment (turns out normal people don't get so distressed over things like everyday sounds being too loud or changes in plans), and as much as I want a life partner, I'm definitely not dating until I can fix this in myself. That said, I'm second-guessing all of my other relationships with friends and acquaintances now. Like, how do you recognize when a reaction that feels proportional/normal to you is actually out of line?