I like this:
Mental health tips. . .
Don't listen to the little demon in your head that says you can't do this. You can do it, you will do it, in fact, you are doing it. If you've been accepted on a phd then your supervisor, your institution and your funding body (if you have one) all believe in you; so make sure that you remember to believe in yourself once in a while.
Your thesis does not have to be perfect, it merely has to be good enough (although this is still difficult to achieve, it is infinitiely more achievable than 'perfect')
I borrowed it from the postgraduateforum