I have the urge to choose to go to my friend's birthday party on Valentine's Day.
What is wrong with going to a friend's b-day party?
I choose my friends over a person who has a severe mental disorder that asked for my help.
If someone who is dealing with a mental issue asks for your help, it's not okay to blow it off and go to a friend's b-day party. Let go of your desire to have some fun, and help a person in need.
I don't really care, I have the right to be selfish.
You're right, you have the right to do whatever you want. But that doesn't make you justified in talking down on someone with a mental disorder. Try to put yourself in their shoes and see how they would feel, that may just change your mind.