Pat: You said you would go to the movies with me!Originally Posted by phalkun
Sam: I'm sorry. I know I said I would go, but I can't go now. I have to work late at the office. Sorry.
Pat: I am so upset with you, Pat. You are always working.
Pat: Don't be upset. I will make it up to you. I'll fix the problem. I'll take you to an expensive restuarant tomorrow night, OK?
make it up to you means, to remedy negligence. That is, when you do something that causes a negative result, you can fix it (i.e., make it up) by doing something positive.
All the best, :D