that no matter how unpleasant/terribly unpleasant or horrible unhappy a situation is, to grit my teeth and ride it out.
This is difficult, can be unbelievably difficult, but it is do-able. Ride it out...Ride it out without bitter thoughts either directed to those creating this unpleasantness/unhappiness, or towards myself. And the results are peaceful.
The tactic is this: Do something, anything to keep your mind away and occupied with something else. Do something so that, as it is bound to happen, when your mind does go towards it or veers towards it, you force it away and do something else - keep on at your regular tasks - no matter how much you don't feel like doing anything - read, do some craft work, or whatever you had scheduled for this time, or which gives you pleasure during normal days. Maybe you'll have to re-read what you'd read or redo the craft work again, but it wouldn't have been a waste of time and energy, because it helped you ride out and wait out the unpleasantness/unhappiness.
This helps:
Let every situation be what it is, instead of what you think it should be, and then making the best of it. ~ Walker Samui