I realize this can't apply in every situation, but often, a choice to "accentuate the positive" can change how we see our circumstances. President Monson has always been an example of optimism.

Tomorrow morning, choose to wake up and smile. Sing a happy song as you go through your morning routine. Then choose to be uplifting and complimentary to family, friends, coworkers, and strangers. After that, choose to serve someone. Finally, choose to thank the Lord for all the good things you saw that day. Again, I know that some circumstances can't be overcome with a smile, but when you choose your outlook you'll feel empowered to face the difficulties outside of your control and push through them.