Uzzy, cleansing and banishing are incredibly easy to do. There are myriad rituals to help direct intent. It would also put your boyfriend in the thick of the ritual if he did it himself. His own intent would be directed, but he must be the one who wants to do it; he cannot be forced into it.
I'm hoping you're not trying to change his attitude, such as an anger issue. I can tell you from first-hand experience that takes determination, practice, and training. I read books, learned mantras, learned how to analyze myself when my mood started peaking. Five years later, I am much improved but I have to keep vigilant, lest I slip up.
Or a mood issue, like depression: No spell can just fix that, no matter how much negative energy is banished. That, too, takes a lot of work to manage. I have never taken medication for my depressive issues, as they are not consistently severe enough. But I do have to make sure I work to keep it in check, and a lot of it is similar to things I learned with anger control.
I'm not assuming this is exactly what is going on, but sharing a bit of my tale in case it helps.