What's Commitment?

During the last fortnight, this topic has been in the forefront of my mind: what is commitment? Some people are commited to doing what is right, others are commited to do what is good for them, and other people are commited to what they want to commit themselves to. For me, and many people, especially those with an english background, have a commitment to what they say they will do, whether they like it or not. For example, someone invites me to a party and i tell them i will go. The day before the party, another friend invites me to their party. I would say no to him, and go to the first guy's party because i made a commitment to show up to his party when i said i would go. However, many other people, and i'd say predominantly asian, purely from experience, seem to think they can just say yes to everything and then make up their minds later, and rock up to whatever they want to. This, to me is not commitment. It may do justice to one person, but complete sells out another. How would my friend feel if i promised him a year ago that i would be there for his wedding, but not make it because i found out there was a party on that day a week before the wedding, and went to the party instead of the wedding because i thought the party would be funner for me. This has happened to me on many separate occasions over the past week, and it seems there is a disturbing but reoccuring pattern going on. What is commitment? Doing what you say you will, or doing what you feel like?