OP I fully understand what you are going through mentally. The pressure is intense. The doubts. Squirrel Mother is completely spot on.
Nearly a year on, my child still fantasises that we will be a family again and live in the same house. It's heartbreaking. Our relationship wasn't right, but to other people it probably looked perfect. He had an affair. It was a real shock that we would split up because there were no arguments/hostility. We'd been together a long time and I will never forget my child's face when we told her. She's 9. It's the most difficult thing to see such anguish and shock, offer support when you're in turmoil yourself, getting her used to living between two houses and then came this covid life.
Anyway, my advice is go with your gut feeling. You know deep down this is the right thing to do.
Avoid looking at family photos for a while as that messes with your head.
Make a bullet list on your phone of all the things that have annoyed and upset you over the years. I'd started doing this before we split and gosh it kept me sane whenever I had doubts. I still review it. It's therapeutic and a stark reminder.
Now I'm glad I don't have to deal with him on a daily basis. I think when you are focused on family and not yourself it's easy to push your own happiness to one side.
Still struggling with my child's sadness though and it's extremely hard on the days that you don't see your children. That doesn't feel right because that's been your life. I'm not going to lie, combined with covid measures this has been a very lonely time. It's a grief - a part of your life died - but better times will come.