Weird! I thought I was the only one who was like this; no one understands it when I explain it to them. I can get shots, look at needles, even handle the sight of my own blood to a small extent, but I cannot watch it being drained out of me!
Last time I had blood taken for a test the nurse got the needle in and said “The bad part’s over, you can look now!”
I told her the needle wasn’t what bothered me and she said that she had never heard of that.
I’m CMV negative and donate on a regular basis. It is a bit inconvenient but the bottom line is that blood donation is necessary for people to live. And I feel privileged to be able to donate.
You chickened out today. There’s always tomorrow. 
And I am so glad to have read this from two of you as I previously thought my spouse had made it up. (He is sort of a drama queen).
He can’t even watch other people give blood, but is cheerily not freaky about needles. He just mutters something about blood belonging on the inside and not being sucked out of you into a bag and goes to have a lie down.
But he can donate blood if they put the bag behind the chair where he doesn’t have to see it.
I don’t get it; but then he doesn’t get my little medical quirk. I have an unnatural fear of *not * being able to see instruments about to be used on me. I have to watch them put the needle in or I freak out uncontrollably. Seriously, I have to see them or I imagine far, far worse.
I know why this is, though, which also helps keep in under control. I have no idea where Dearly Beloved got his peculiar notions and neither does he.