If it is a technical problem try really really slowing it down. Be sure the fingering is secure and written it. Study professional recordings while watching the score. I find this really helps me. Keep playing your scales, chords, and arpeggios. Enjoy listening to them getting stronger week by week. I notice a big improvement in my drumming every 100 hours or so of practice. That’s about 4 times a year! My teacher though hears small improvements weekly.
If this is a reading problem start clapping the rhythms and counting out loud. Practice hands separately. Work on improving your sight-ready by regularly starting your practice sessions with it. Reading pieces off www.musicnotes.com is fun. Lots of popular music, first pages are free.
If you have a motivation problem maybe you are playing the wrong music? Or, you have too many conflicting activities, or your goals are too big for the time available. Or, are you too focused on the results desired instead of enjoying the journey to it?
You've got to learn your instrument. Then, you practice, practice, practice. And then, when you finally get up there on the bandstand, forget all that and just wail.
I'm a professional pianist and music educator in West Toronto Ontario. I'm also a devoted percussionist and drum teacher.