I'm a full time student who's working full time too. I know how strenuous it is. The spring semester is far more stressful than the fall! Anyway. I too am the type of person who can't say no, and everybody knows it. The problem with that is that everyone tends to ask favors, and you end up with no days off...ever. Eventually it just builds on you and you're sleeping less and you become irritable, and then you find yourself being resentful without even intending to. At least that is what happens to me at times. I find that when that happens, no matter what...you have to arrange for a day off for yourself. You cannot run yourself into the ground every day for weeks on end without it having a horrible impact on you as a person. So my advice, no matter how unfeasible it is at this point in your semester, arrange for a day all to yourself. Shut your phone off. Stay away from people if you must. But rest up, and have some fun. Let those worries and stresses out.