Bad luck on the Canada girl, I think I remember posting some advice at the time - obviously not great advice, but hey, you obviously recovered well.
I have noticed this exact same thing. Treat girls like shit and they keep coming back, be even a little affectionate towards them and they take you for granted. Ok, so thats fairly general but its true. Do be careful though, it isn't far to hurt girls. If you want to date a few women at a time that's fine - just make it clear that you aren't in an exclusive relationship with any of them.