Hey possiblyadd, you’ve come to the right place. Relationships are tough and being in a relationship with someone who is ADD can be really frustrating for people without it. If you do not want to be medicated (Wellbutrin and Vyvanse are good options if you don’t want to feel whacked out), then I suggest starting Cognitive Behavioral Therapy. You may require a therapist to get you started but it’s pretty simple. Look it up online, it’s basically a practice in being present and aware without any vague spiritual requirements and dogmas.
Remember too that your wife should easily forgive such benign shortcomings in the grand scheme of things. I mean, at least you aren’t an alcoholic like me. There are far worse problems to be having than unlocked doors. If your wife continues to harang you, consider there might be an underlying issue (not necessarily with you). This is important. From my experience, neuro-normative people often find it easy to blame people with ADD for their own problems and anxieties. I’m not entirely sure why this is, but it happens wherever someone with a disability or behavioral difference exists. This scapegoating is a major defect of neuro-normative people. They don’t self-doubt and self criticize as much as ADD’s and depressives. And when they do, they have the nasty habit of projecting those negative feelings onto someone who is more susceptible to criticism and who makes careless mistakes (i.e. us). This is why untreated ADD can be harmful: you will begin to believe that your inability to complete simple tasks is a result of deeply rooted moral/behavioral/character flaws. This is dangerous because instead of giving you the tools to overcome these challenges, you are made to believe that you are inherently and indelibly broken.
Give yourself a break. You don’t sound even remotely like a failure and if leaving the car unlocked is how you fall short of perfect, then you have it better than most. Again, I think it’s more an issue with your wife or that you haven’t adequately explained your feelings about the situation to her (i.e. that her criticism cuts deep and that you are really struggling to be better and that you understand that it seems like you aren’t making the effort to change).
Best of Luck bud, Let me know what you decide to do.