WHAT WOULD YOU DO?

I wonder what makes people think it's okay to cancel plans at the last minute? Here's the rub, I made definitive plans with someone, got out of my shift at work to attend this event, and 30 minutes before it starts, I am told that they already had plans with someone else and that they have to cancel. Great. Thanks. I possible could have asked someone else to attend this event with me had I ample notice. What exactly is it about me and my personality/character that makes you think it is perfectly acceptable to flake out at the last minute? This isn't the 1st time either. Lesson: never make plans with this person ever again? How can I let this person know in a positive way that they are continuously hurting my feelings, disappointing me, & pissing me off simultaneously? I have refrained from going off on a verbally abusive belittling rampage like I initially wanted to, because as we all know, it will do no good in the end and actually would probably cause some serious damage to our relationship. So I ask you, world wide webbernet, with all your tubes & wires & such...WHAT WOULD YOU DO?