Since I was a kid, I have been a big complainer. I am bit fussy over everything and am very hard to satisfy(non sexual reference). But I maybe one of the few people I know who believe sincerely that if you are not satisfied with what you have it will drive you and motivate you to want more and more.
Being happy is the worst thing that can happen to you. Can you imagine those mornings when you were truly happy, you don't care about anything. You take in your breakfast slowly,read the newspaper and slowly go to work. Chances are you will be fired within few months if you enjoy your life so much. Also remember the time you had a girlfriend and you were really happy. You did not care if you lost your job or lost your friends all because u were really satisfied. In every direction you looked , you only saw her face. That illusion did not last for long and when you hit the ground really hard , you realized you had even lost the quality of motivation.
I believe being hungry, dissatisfied and having your back against the wall would be the best thing that can happen to you, because if will uncover the sheer willpower you have to break free from the rut. Many people instead of trying to break free from the prison of misery they are in permanently try for a temporary solution with tiny things which might cause them temporary pleasures. Also this illusion does not last forever and you end up at the place you started from, this time even more de motivated because you have the illusion of trying different things(tiny pleasure solution) and failing to achieve the happily ever after.
In conclusion, the best thing is to look facts straight in the face, and see how miserable your life is and how you want to change it. This is the only way which can get you out of the job, relationship or any other situation which you hate so much.