Other forms: imperturbably
If you're imperturbable you are not easily upset. If your goal is to be imperturbable, then you can't let things bother you or get you stressed, confused, or angry.
The adjective imperturbable is the flip side of perturbable, which comes from perturb, which in turn traces back to the Latin word perturbare, meaning “to confuse” or “to disturb.” If something really annoying is going on, like one neighbor is jack-hammering his driveway and another has a dog that's barking while you're trying to sleep because you were up all night studying and you really really need a nap, but you stay calm and don’t get upset, you are imperturbable.