Never quit a job unless you have something to replace it. Why?! You never know how long you could be without that income. I know it sounds so simple. I understand about being miserable and treated like crap, but have you actually sat down with the manager and talked through everything with him? There might be a justified reason he did what he did. Sometimes, you have to take a step back and look at the bigger picture and try to keep your emotions out of your decisions so they aren’t impulsive and rash.