Your birthday signifies the gift you've been given from God and from your folks.
The gift you've been given is you being alive.
To really celebrate you getting older, you can and should have pride in you being 1 year older - you've made it, you're still alive and physically healthy.
You celebrating you being alive either by yourself, or with those you love in your life will make you very healthy in your mind.
When you feel healthy in your mind, you'll find you stop getting physically ill, or having pain in a part(s) of your body.
When you have physical illness / pain in your body, this is your brain trying to take the pressure and stresses off your mind's plate.
It's a nice theory that perhaps works, but I don't know about you, I just find it a pain in the back side. One feels a tiny bit less stressed about a problem in one's life, but one has to sort out a physical problem now too. I feel like saying to my brain "come on brain, get rid of the pain in my back, I think & I feel I've got enough things to sort out in my life".
Thank your brain for being so healthy it's able to try to help you out.