Mine are:

1. "It is what it is."
2. "I am a sensitive person who sometimes sees the world differently."
3. The Serenity Prayer: "Grant me the serenity to accept the things I cannot change, the courage to change the things I can, and the wisdom to know the difference."

If I am having a distracting, unfocused, and unproductive day or am nervous about starting a project, I use the mantra: "Stay focused and know you will be successful." My T told me it once when I had to get major paperwork submitted by a deadline, and it REALLY helps me!!