From Longman Dictionary of Contemporary Englishrelax your concentration/vigilance etcrelax your concentration/vigilance etcATTENTIONto reduce the amount of attention you give to something → relax
Examples from the Corpus
relax your concentration/vigilance etc• Once they lose those bright feathers they can afford to relax their vigilance.• Take care not to relax your concentration on the way up. 2.• I forced myself to open my fingers, to relax my vigilance, to fall asleep. 