People! ADHD is not a valid excuse for hurting someone, nor is the person who was hurt under any obligation to “understand” that you have ADHD. Breaking a life-long promise to your supposed most important person is a betrayal that can’t be undone. There’s a level of trust that will never be restored, especially if all you offer is excuses that basically make it clear you don’t intend to take responsibility for your actions. This isn’t about missed appointments, not helping enough around the house, and an inability to keep organized. This is someone’s heart that was broken, and dream shattered, and trust lost.
The treatments available for ADHD are very effective when followed. Given that, you have no excuse.
You want to be forgiven? You want to repair the marriage? You want your spouse to understand? Then make a commitment to yourself to never do it again, and to follow a proven treatment plan. And stick with it. Show through your actions that you have learned your lesson and have changed, that you feel remorse and never want to cause that kind of hurt again. And you should understand that if you are forgiven, it will take as long as that person needs to feel ready to forgive you. Could be years.
Otherwise, do your spouse a favor and let them out of the marriage without a hassle. It’s better not to promise than to make a promise you don’t intend to keep (or that you’re unable to keep).