Many of us constantly complain about our jobs. Even the happiest, most satisfied employee will occasionally find something that needs improving. This is a good thing for two reasons.
1) The most obvious: complaining about your job means that you are employed. This means that you have an income, no matter how small it may seem, that can help you put food on the table and a roof over your head. I know that not all jobs provide enough to even live comfortably. However, something is ALWAYS more than nothing.
2) If you have something to complain about at your job, then that means that you have an opportunity to help your organization grow and improve. Organizations are organic--funny how that works, huh? That means that they need to keep learning and growing, improving and changing as a system if they want to survive (and maybe even thrive). Much like a human's personal journey on the path to self-improvement, the best way for any organization to grow is from the inside. Embrace those things you complain about and try to look at them as windows of opportunity to make things better and more efficient.
Of course, if the job is too abrasive, too much for you to handle, go on the job hunt. Just remember to secure a new job before you walk away from the old one. Something is always better than nothing. Plus, unemployment payments don't last very long.