Does Visualizing Work?

So I have this hugeeee swim meet coming up on Friday, and jeez I am freaking out. I heard that if you visualize yourself swimming or whatever you'll feel better. So I was sitting in my chair, 'visualizing' myself in the pool and all I saw was Dive, Dive, Sink, Sink, Drown, Drown, Drown, CPR. My coach says I don't have good mentality. First I had to look up the word mentality. And then I decided he was right. I don't have any kind of confidence either. But who would? Once you see everyone in all the other lanes far far ahead of you, you don't exactly go, OMFG I COULD TOTALLY WHOOP THEIR ASSES FROM 20 YARDS BEHIND THEM. No. Not at all. You're just kind of like whoop-de-doo, whipped from the start. Then you pass out from being so tired and then you get yelled at for disappointing yourself and everyone else, then you cry a little and then you're like "Damn, shoulda done soccer." I am in no way looking foreword to this swim meet. But the bright side is that hey, if I drown, maybe a hot guy will give me CPR, right?