Here's why "a spell" will not work: Improving a compulsion is not something which can be wished away. It is a process. It is not something that therapy can change for you. It is something you must work to change. The medical and behavioral therapies can help, but it cannot make you change; you have to change you.
This is also where magic can help (but it it not a cure, mind you). Meditation, self-analysis, doing your own behavioral analysis: these things can lead to improvement.
Changing your behavior deliberately is the change which you seek. Every time you respond a way, you reinforce that neural connection. I have anger issues. It is not a compulsion like OCD, but it is something I let go unchecked for the longest, and used every excuse imaginable to not take responsibility for my own actions. I eventually had that 'moment' which opened my eyes to the need to change.
I bought books about anger, started meditating (I had tried for fictional 'magic' purposes some time previously, but this was different). I learned visualization exercises that worked for me, breathing exercises to bring myself down, and mantras to let go. I learned to analyze my own behavior, and stop it at some point to not be angry.
It has been years, and I am a lot better than I used to be. It is still a process. Whenever I meet one benchmark of progress, I move to the next. And as much as correct behaviors are reinforced, the bad behavior still lurks at the corners. I can let go of anger much more easily than I used to. Many things no longer phase me. So I am focusing on some other issues which are now at the forefront.
This is partly the "magic is psychology" mindset you will see some people talking about.
Magic is often defined as change in accordance with one's will. Creating this change in accordance with your will can be a very long process. Deliberately changing your brain is not easy.
But improvement can be achieved, and magic can be used to help the process.