Sometimes you have to say no to friends and they don't really understand.
When you write on the side, friends think of it not as your job but as your "hobby" and they just don't get it when you have to say, no, I can't go do that with you, I have to write. They really do not understand. You should be able to just toss your hobby aside to pay attention to them.
It can be frustrating. And sometimes, you have to cave and say, okay, I will do that. Just don't do it too often. You must write to be a writer.