Don't beat yourself up. In todays economy we are lucky just to be working. Instead of thinking of things in a negative light- try to think positive- if you work alone try getting an MP3 player of some sort with your favorite music and mix it up once in awhile...take a walk, or go to a park on your break time-being in nature is simple medicine.
In the meantime, you can look for work else where while still keeping your current job. Tell yourself, that this is only a temporary situation- because you have the power to change anything you want to in your life. We all make mistakes the thing is to learn from them...and I am sure you are quite educated to see the writing on the wall. Get out the crayons draw your own picture and before taking the next adventure make sure you are prepared for what YOU really want. Hope these few words helped a little.