BD depressions are the best, it won't get easier, so you might as well get used to them.
Really the best way to not overthink your birthday is to travel or have sex.
Going to dinner and events with friends help too.
This year I did massive things not to think about my birthday and it was alot of fun.
Night before my Birthday i went clubbing yeah sure a bunch of 21-year-olds, but I got my patron on and saw some old peeps On my birthday. I was determined to be active. So I did a puzzle room, hiking, waterfalls, cheap dinner, bowling, it was on a Sunday, but still, it was fun.