Occasionally I come across sayings, though that word doesn't do them justice, that I really like and embrace, like:
Boredom is a choice
Dance like no one is watching
You are responsible for your own happiness
I really like those. There is another one that I have always been interested in, but either didn't understand or maybe agree with, so I've modified it a bit.
That which doesn't kill you or anyone you love, makes you stronger and should be looked at as a positive experience, no matter how tough it is to go through at the time.
Kinda clunky, but it's something I'm going to try to remind myself of when something is really affecting me negatively.