Learning to deal with frustration is probably one of the most important skills one can acquire.
Then, constructive perspective there where there is space for action; just stopping wasting energies on it where there is no space for action.
if things aren't going your way, and you are ruminating and poisoning your blood fruitfullessly remembering the bad events, replace those thoughts with the acceptance that the events are there - stop agonizing uselessly, take the novelties as just a matter of fact. Get out of the thought, get out of the emotion - they can be replaced by a label, "Past. There. What is done is done. Next".
Then, if you can do something about it (to fix the situation), enter the constructive mood of the entrepreneur exploiting the useful fact of being alive to engineer reality. Otherwise, if you cannot do anything about it, bear the consequences but do not let the damage increase through an inadvisable behaviour of possibly letting events impact your mental, emotional states - that would be wasted energy, wasted health, wasted time.