The first is from a small placard an ex-manager gave me, when he left our group (He was a great guy!).
Try is a big word. If you try, you risk failure. If you do not try, you ensure failure.
And the second is from the Empire Strikes Back (Starwars), and said by the Yoda.
Try not. Do or do not. There is no try.
Credit for the second one goes to todays post in Zen Habits.