Say sorry fast. Forgive yourself slowly if you must, but do it.
When we've hurt someone, the best thing we can do is apologise quickly. Not a long defence. Not "I'm sorry but." Just a sincere "I'm sorry. That was wrong."
The harder part comes after: forgiving ourselves.
Some mistakes stay with us a long time. That's okay. But forgiveness has to arrive eventually, or we carry the weight forever and it poisons how we treat everyone else.
Say sorry fast. Then start the slow work of letting yourself off the hook.