Honestly, I don't think that's true confidence. If you're worried you're giving your power away then you don't believe that you have a lot of power to begin with. That means that you don't really have confidence; you're just lying to yourself. Sorry if that's what you don't want to hear, but it's the truth.
Listen to Pickuppodcast, they explain it pretty well (the 3-part series on Value).
You can't base your confidence on you being better than anyone else; that's just arrogance. And arrogance is used to cover up insecurities.
Oh yeah, human relationships are based on having the power over another person; but using it in a way that benefits both. Alas, she doens't really have any power over you; is she so important that by "giving your power in her hands" you lose it? Nah. If she turns you down: WHO CARES

. Talk to the next one, start over. She doesn't have any power over YOU, only over HER. And it takes two to form a relationship.