I'm a week from turning 19 and I've been having so much anxiety over it . I've always been kind of indifferent to birthdays. Don't get me wrong, I love going all out for other people, I absolutely loathe my own. Why? Because it's literally everything I hate wrapped into one.
For starters, I have struggled with social anxiety since I was a kid. I don't want a disorder to affect my life. So the best way to do that is to avoid anything that triggers it if possible. This includes parties, large gatherings, being the center of attention, people "ooing" and "ahhing" over me, etc. This is pretty much all a birthday is.
If someone casually sends a HBD text or just says it once when they see me, that's cool and much appreciated. I just hate when people try to make a huge deal when I ask them not to. For example, constantly asking what I wanna do or saying HBD everytime you see me. Ofcourse you have the occasional "Oh let's _____ *insert something that person wants to do* because it's MY birthday. 
Don't get me started on restaurants. Having a group of people, especially strangers, sing to me sounds like a nightmare. That's basically giving me a panic attack as a present for my birthday.
Putting me in the spotlight of anything just gives me unnecessary anxious tendencies. I'm not trying to be mean or spit on other people's excitement, but not many really get it.
I know people are just trying to be nice. However, when I specifically ask them to not do something and they do it because "it's your birthday" and "we needd to celebrate" I don't appreciate it. Infact, I fucking hate it. Overall, I just wish it was treated like a normal day. I don't know why I have this anxiety or what causes it, I just wish people would be respectful and not try to make it about them. Overall, I just wish it was treated like a normal day. "Congrats on living another year" and just keep it moving.