In addition to previous suggestions:
Learn to breathe into and out of difficult passages. This is not as easy as it sounds. I have to practice this technique and I write it on my score, just like any other fingering or dynamics indications. I usually have to highlight it with color because if I'm nervous during performance, I often will miss it! It is best to breath with your mouth slightly open since it forces you to relax muscles in your jaw, neck and shoulders.
Practice at varied tempi, alternating slower with faster. This builds resilience and, like some one playing sports, teaches the body and brain to learn multiple strategies to cope with various (and sometimes unexpected) experiences playing the passage.
Work on left hand finger independence. I truly believe that the ability to apply and release tension at will originates in left hand flexibility and finger independence. Time spent working on this for a few minutes every day is time well spent.
Wishing you all the best,
So much music, so little time.