I have used the following approach in my practice over the years and have seen many students get quick results the same way. There seems to be a reluctance and aversion to all 3 of these methods. Maybe it is intrinsic in human nature to want to struggle and to speed. I don’t want to delay any longer because you are probably at least a little curious.
1) Slow down!
Like the other 2 ways below, this would seem obvious. I have found that even after repeatedly asking my students to slow down when they are having difficulty, there is something about their frustration and adrenaline that makes them get faster and faster. If you can’t control your tendency to rush as you are practicing, a metronome set with some subdivision can help to keep you honest. You can also slow down to a point of playing rubato (or out of time) when addressing some technical, coordination, intonation and other issues. There is no shame and no limit to slowing down. If you want to play fast, practice slowly. You can incrementally increase your tempo and by the time you are at your goal speed, you will be playing accurately and comfortably.
2) Count down!
My first private teacher (on drum set, snare drum, music theory and Vibraphone) was named Casey Casino. Mr. Casino was "old school", thorough, no nonsense and placed an emphasis on foundational musicianship. He would not allow me to play on any instrument without counting out loud. After a while, it gets so ingrained that when you are performing and there is any need to keep track of difficult passages, you are counting in your head automatically. Counting out loud while practicing and working things out provides an awareness and an audible reference that is so helpful. Some of my students insist that they are counting in their head, but when I insist that they verbalize what they are hearing in their head, it invariably comes out as an indecipherable transmission from a distant planet. In other words, you don’t know what is happening in your head during these times unless you utter it. Mr. Casino said count out loud and it has served me well ever since 1971.
3) Break it down
There are so many ways that you can break a challenge into smaller pieces. The first step is to identify where the problem is happening. The more that you zero in, the more efficient you will be. On the drum set, you are playing 4 limbs. Sometimes it pays to practice the 2 hands, then the 2 feet, then the right hand and right foot, etc. Sometimes it is effective to break things up in a linear manner, where you are practicing pieces left to right incrementally. If you had a big steak in front of you (apologies to my vegetarian friends and readers), you would never think of picking up the whole thing and shoving it in your mouth. There are infinite ways that you could cut it up and some people cut their steaks into mighty small pieces. It assists them in consuming and digesting what is front of them. It is the same with musical matter. Use your discretion to confront difficult musical challenges in doable bite-size steps.
I believe and have seen evidence with countless students, that these 3 strategies will get you satisfying results in your musical journey.
Give it try!