Relaxation techniques are “quick links” to your brain’s built-in ability to relax you. There are many types of relaxation techniques. It is primarily a matter of finding which are most effective for you. So try out a few and see which ones work best.
Then practice, practice, practice. The more you practice a technique before you need it, the easier it will be for your brain to quickly recognize that you want it to relax. That way you can counteract periods of high stress with your favorite relaxation technique when you need it most.
Don’t wait until you hit a rough patch before you decide to learn a technique. When you are already “stressed out,” learning a new technique is much more difficult.