How do I psychologically alter a subconscious dread for work?

Here is a little background: I've returned to school as a full-time student and I currently have the summer off. Ever since last summer when I took up a part time retail job I have developed a weird and infuriating hang-up: if I know I need to work the next day, even in the evening I cannot fall asleep. This summer I have taken up a part time job at my local public library and it's happening again. I anticipate the work somehow or, for some strange inexplicable reason, I think I dread it. I become so anxious that not even a glass of wine will settle me for the evening. This is becoming ridiculous- my shift doesn't begin until 1pm and it's only for three hours! Is there something I can do to rewire my viewpoints or subconscious preconceptions of work so that I can sleep and proceed my employment as any other "normal" person? I want to nip this in the bud now so that when I begin my permanent full-time career it doesn't effect me and I can enjoy sleep and work again.