Why don't you start doing small things that make you feel good about yourself? Even small things like going to sleep in a made bed, next to a notepad, a pen, and some water. Small things like this help me get any ideas or dreams out for further analysis and waking up to water is just good. I feel better to even make my bed. I've been reading a lot of self promotion/improvement and healing lately. Usually I'm a pretty negative person. But recently I've been trying to catch myself and replace negative thought or comment into a positive one. Like getting dumped. Something better is gonna come along, but we all have our hiccups. Some more then others.

As for a simple forgetfulness of a "thank you", I think small things like that can easily be caught and fixed. It also never hurt to apologize and thank later. Most people are more understanding then you would think.