One of the best tools for your practice is your voice. Faced with a tough part, if you sing it, you’ll be able to play it better because you’ll be able to hear it better. Singing the passage allows you to “own” it in a deeper way than by pushing buttons or keys on your instrument. This is just one of many strategies you’ll find in The Practice of Practice.
You don’t have to be a great singer to benefit from this kind of practice, but here’s a couple good videos on vocal tone production and breathing. If you’re a wind player, the breathing video is something you should know (and do). Make singing and chanting rhythms for tough sections part of your daily practice. It’s one of the best ways to get better faster.