I find it hilarious that people all over the web want this as a tat or whatever and it was originally intended as an insult. Shakespeare, Midsummer Night's Dream, Helena, Hermia. "And though she be but little, she is fierce."
You can do anything but not everything quote - daily mantra - It's National Stress Awareness Day. What is Your Mantra For Dealing With Stress? Answer here: http://www.levo.com/posts/what-is-your-mantra-for-dealing-with-stress