What if I do this? I'm going to skip out on my friend's birthday celebration.
Ohhhhhhhh, my gosh, you are so not going to do that are you? Why would a friend do that?
I've decided that I don't like the person anymore.
Did you literally just decide that you don't like them anymore? Skipping out on their birthday at the last minute is not nice. How would you feel if they did that to you?
They did this to me.
You still have a friend though, so why would you risk losing them over a silly thing such as a birthday? Maybe they can make it up to you at other times of the year? They could have had other problems on your birthday.