I do the same. It's like I have a sliding scale from best friend to acquaintance. I had someone I considered a best friend slide to the acquaintance end of the spectrum because I keep making lots of arrangements to meet and she cancelled each time. It happened 3 times and the last time I thought, right, that's it. Not that I'm cutting her out of my life, just that I'm not going to make an effort if she isn't. She still says "we must meet for coffee" but I've since discovered she does that to everyone close to her, but never does. All her friends know she's unreliable. So she's less of a friend in terms of closeness than she was. But then I have other people who move from being a casual acquaintance to getting a lot closer too, as they initiate meeting up. I try and think of it like that, because it stops me from feeling upset if I'm let down - and it means I'm open to developing new relationships.