How do I change my negative views of men/relationships?

I know not all men are liars, cheaters, players, manipulators,or come with ulterior motives so why can't I go with the flo and enjoy the moment without the anticipation of being let down, betrayed, cheated on or taken advantage of. The interesting thing about it all is I've never experienced any of these things with a man before. So my past isn't the issue however my single girlfriends have experience all of the above pain and more. When they hurt I hurt which is why I feel the way do. I bring the drama! How do I change?