I sympathize. However, no matter how much you build it up in your mind, an injection is over and done with extremely quickly. You don’t have to force yourself to do anything for long. Take it one step at a time: force yourself to go to a pharmacy. Then force yourself to talk to a pharmacist. The only part about getting a shot that involves actually getting a shot is extremely brief. Up until that fleeting moment, you might as well be picking up some shave gel or chewy vitamins. (Lots of places offer you store credit or a gift card for getting a flu shot – that’s a fun new Nyx eyeshadow color you get to try for free!)
Very thin needles make it more bearable. Some people have reported that Target pharmacies use thin needles. The downside is that the injection can take a little longer, but you barely feel it. Be sure to tell your attendant that you have a bad needle phobia.
My method to handling shots without going full convulsive vasovagal syncope has been to distract myself. If, like me, you tend to collapse or convulse, tell the pharmacist and you can get the shot lying down. If you tend to infodump, my nurse looks forward to hearing everything there is to know about axolotls. I also sometimes prepare a YouTube video to stream while I get the shot. It can help to call up a friend on the phone and have them talk to you.
Two words: gaming apps. If you’re concentrating on Fruit Ninja or Tetris or some other timed games, your brain has less ability to panic or even notice that a shot is happening.
Also, pediatricians tend to be able to give really fast shots because they deal with babies.