I'm too much of a "nice guy". Any protips from former nice guys on how to improve my cockiness/confidence/dynamicness?

I'm definitely one of these nice guys right now. I especially suffer from the over-analyzing and passiveness...I gotta learn some more cockiness and confidence. I guess I am just a bit of a pussy. I'll go up to girls, but its always ends up being too friendly conversation, not really getting me anywhere.
But its kinda a circle for me, I feel like I'll be more confident once I start having more success with the ladies but I haven't so its stayed the same, any protips from former nice guys?