The saccharine "you're never given more than you can handle" is hardly helpful when you're staring down a void of suffering; even when the comment is well intentioned. But there are tools and tricks you can use to bolster your own mental toughness when you're feeling anything but.
1) Focus solely on what you can control - What can you do right now with the hand that you're dealt? Can you change it? Probably not. So stop wasting precious resources on futile efforts. Pouring yourself into making your new norm something extraordinary is a badass way to deal with adversity, so get to it.
2) Make every action positive - Take whatever negative you're dealing with it and drown it in all things good. Give your attention to the things that are going right and celebrate them. Not every day is good, but there is good in every day.
3) Be unrelentingly consistent - Sometimes it takes a major event to snap us out of our funk and start focusing on the positive. But that doesn't mean your gratitude practice stops when you've put that initial catalyst behind you. Being mentally tough isn't just about dealing with the extremes. It's really about how you handle the every day stuff like the commute traffic and picking the "wrong" line at the grocery store... again.