I thought everyone could understand what Yoda was saying when he said that. He's saying that how you mind things is very important, that if you are going to succeed you have to believe you can. Trying isn't enough. You're either going to do it or you're not. There is no trying. Trying is not an absolute resolve or complete mental discipline. To say "I'll try" is a form of inner self-doubt, and it's what Yoda is trying to remove from Luke so he can progress.
He teaches Luke this as part of his Force training, and to lift his ship out of the swamp. Luke was unable to because he failed to grasp this principle and believe it was possible, so Yoda had to do it for him. While Luke failed the test, he was still taught the lesson and understood it, which is what mattered.
Like I said, I thought everyone knew what Yoda was talking about. 😛
As for the last post, you said "young vampire", when theres nothing young about me. I'm the oldest vampire there is. The original. 😛
As for coincidences, I'd say its a big coincidence in that Buffy is a vampire slayer, and here I am. 😛
