valentine’s day without my ex advice

tomorrow is the first valentine’s day since our breakup I won’t be with my ex. he was my first love and even tho it ended five and a half months ago I am dreading tomorrow because I still do miss him. it makes me feel awful thinking about how a year ago I was so happy with him and things are so different now. I am going to dinner and hanging out with my friends and such but I thinking deep down it’s gonna hurt me all day. how do I get through this? anyone have any advice? it just makes me feel very sad and nostalgic.