I collect motivational sayings and post them all over the wall in my workout room (as soon as my son moved out I took over his bedroom!) Every morning when I go in there to exercise I see all of these motivational quotes and photos, and it reinvigorates me.
For race days, and other challenging days, I write on my hand:
NEF (No Excuses, Finish)
You are better than you think you are and you can do more than you think you can.
Just don't tell my mom I write on my hand!