How to undo damage of slapping cat?

I recently got a kitten, and I had been disciplining him by smacking him on his side. I believe he's part Bengal, and he's extremely hyper, getting into trouble frequently. I read that you shouldn't slap them, but use a spray bottle instead. I also read that cats never forget. Is there anything I can do to repair my relationship with him? He still lets me pet him, and he purrs around me, but sometimes he runs away. Help?