Scared to Quit Job?

I am working 80+ hours at my current job as an event coordinator. I enjoy event coordination, but not the hours I am working. I applied at a different event coordination position, and received it. Now I have to tell my current job that I want to quit. I have spoken to my boss a couple of times about getting someone else, and they are going to hire a person to help me and my collegue for only 20 hours a week. I think we need to hire another person, full time or more, and that is what has driven me to look else where. My new position is 40 hours a week and pays the same. Why am I still stressing over quitting my current when it seems SO obvious why I am quitting. Is there some easy way to bring it up with my very controlling, unnapproahcable boss?