Geez, I am totally like that! I am an excessive texter, IMer, etc. I want a response right away and I'll check my phone every five seconds (literally). I don't usually get angry, I usually get depressed. Because I think that they're too busy with other things, and they have a life and don't have time to respond to me, and I come up with all these reasons. And it's not that the person doesn't care about me, it's just not everyone obsessively checks their phone! I've been working on this a lot and I must say I have improved greatly!
I definitely know the feeling.