do you practice with a metronome?
a metronome can be useful, in certain situations…
for tricky passages, i think it’s very important to play it VVVEEERRRYYY SSSLLLOOOWWWLLLYYY at first. find a tempo where you can get all of the notes, with the right rhythms, change positions comfortably, use the right technique, etc… it should be slow enough for you to pay attention to everything.
then, gradually increase the tempo. but don’t go too quickly! at each tempo, make sure you practice enough so that you know it in your sleep. if you find that you’re starting to make too many mistakes, that means you’re not ready to play it at that speed. so decrease the tempo and go from there.