Control your breath. Be conscious of your breath and you control you response to life, for the most part.
You can live but a few minutes without breath, a few days without water and few weeks without food.
When it comes time to survival, breath is the last thing one thinks about.
Breath calms you down, reduces blood pressure, enhances focus, ensures endurance, improves performance.
Breathing is the easiest thing in the world, yet one of the hardest to master.