im thinking of using some calvin and hobbes quote.  two of my favorites have to be
"There's never enough time to do all the nothing you want."
and
"To make a bad day worse, spend it wishing for the impossible."
and this one's another one of my favorite quaotes from calvin, but i wouldn't use it as a senior quote.
"I think the surest sign that there is intelligent life out there in the universe is that none of it has tried to contact us."