How to get over my fear of needles..?

I've gotten quite a few needles within this year because of an adrenal problem I have. I know what it feels like and I'm going to be getting blood drawing at least twice every year for the rest of my life. I still panic when the doctors tell me "We're going to need some blood tests.." but by the time the nurse gives me the needle she tells me "You didn't even flinch". Why I am I so afraid still? I know I'm kinda young and It's natural but shouldn't I be over this?