Stretching your glutes (or bum if you will) will help relax your entire body and is something you should do as often as you can.
Rest your left ankle on your right knee and press the left knee away from you as you bend forward. You will feel the stretch on your left buttock.
You can also with your right hand grab on to you right leg and pull yourself towards the leg. Try not to arch your back too much as you do this. Switch sides!