Reliability

Some of our friends just aren't reliable. And I don't understand it! I mean, maybe 3 times in the past couple months I have forgotten about a commitment, and not gone to something I said I would. But I write things down, and when I know that they are important to other people than I put more emphasis on them so I MAKE sure they don't forget. But can I really expect my friends to do the same? or is it my job to call everyone I know the day I'm having something to remind them not to let me down? Well they are (Letting me down, that is) and I don't appreciate it.