gird your loins

Gird your loins is the idiom which is related to preparing yourself mentally to do something you know will be difficult. This phrase comes from the Bible, where girding up your loans meant to tie up long and loose clothes so that they are more practical while you are traveling or working. If you are girding your loins, you are making preparations for something coming up that is going to be difficult, and these preparations are providing you some sort of protection.