How can I not feel so nervous about starting my new job tomorrow?

So I just got a new job and I haven't been working since February, 2016. Since I lost my other job my self esteem has been just a complete disaster. I have been constantly dwelling about my new job offer I received through a temporary agency since Friday. I have great vibes about the position because I do have relevant working experience in the industry for 2 years. I also have anxiety- I feel SO nervous and uptight about starting tomorrow and I can't seem to just relax and enjoy myself. Is there anything I can do to ease up my mind and not worry so much about tomorow? Thanks.