Worries put pressure on the physical body. We should do our duty, and also against opposition, but we shouldn't worry too much. It's hard to strike the right balance here between concern and standing above it, but too much worry dries out the brain so that it can't take in new thoughts.
The greatest man of sorrows or soter was Christ, and as it says in (I Peter 5:7) we should cast all our care on him; for he cares for you. That is, we should give all worries past a certain point to Christ so that He can make our physical body healthy and strong, so that our soul is also healthy.
-Rudolf Steiner, from the Contents of Esoteric Classes
Esoteric Lesson: Kassel, 6-27-1909