Is it just me and my obsessive personality that I can't seem to totally let go of the influence of the people who aren't already present in my life?

My former friend's birthday is today/tomorrow May 19th and I feel like that day is somewhat a burden that I have to endure for 24 hours when it's not even obligatory in my part to make something out of it other than it being her birthday since she's not anymore a friend of mine...

I really hate this feeling... I hope to talk this out with my therapist the next time we have an online consultation...

I feel weird and ashamed to confess this feeling about someone else's birthday and the bad effects on me... Just like to know if anyone also experiences the same or just will give me advice on this...