It sucks having people let you down. It sucks even more when its something that you've been lookingg forward to for ages and suddenly plans have to be altered. It sucks most when the person that you really depend on is the one that lets you down.
Though you probably cant blame the person. You can never force somebody to do something when they're not in the mood. But can you blame me if I feel this way. Especially when you're led to expect that you can always rely on the somebody. And they'll always be there for you.
How would it feel if that someone says to you 'Aww. I'm just not in the mood. You go enjoy yourself.' How am I suppose to enjoy myself when I've been let down? And the reason that you've been let down is because they're not in the mood.
So don't blame me for feeling this way. It's only expected. I didn't force you to do what I wanted you to do so don't force me to pretend like nothing happened.