The best affirmation I know is: May all beings be well, may all beings be happy.
But if you want to work out your own, you could do the following and then decide:
- Do this metta bhavana (loving kindness) meditation from the Triratna Buddhist Community.
- Do one or two of Tara Brach's guided meditations on Tonglen
Also, when I do my chanting, I invoke the attributes of Buddha nature (Wisdom, Compassion, Courage, and Life Force) and I add Self Love. Then after a while I go through everybody who I want to send healing energy to and simply imagine those people as healthy and happy (like they already have the happy energy of laughing children playing in the garden). So this is another way to do a compassion meditation. And, according to a book I have read recently, The Power of Eight - the healing does get to them and not only that benefits the giver.
Check out the Health page for lots of good food advice including what Gary eats, what Annica tells her clients, and Fred Bisci's advice from 50 years of being a nutritionist.