Quick summary: Pavlov serves food and rings a bell. Dogs salivate over the food. Eventually, he rings the bell without any food present but the dogs salivate anyway. I believe this is called a conditioned response.
Stimulus: bell
Response: salivation
All too easily you can end up with:
Stimulus: Music
Response: Tension
Tension bad, very bad.
How to turn this around? Try looking at the tricky passage but play it in a simple, lyrical style (slow, smooth, totally relaxed). The key is to look at the notes as you play in a relaxed style. You are trying to build this..
Stimulus: Music
Response: Relaxation
It might work. At least it's worth a try.