Apprehensive About A Career Change

I am considering a career change. I have been an accountant for a construction firm for 15 years. Lately, I am not feeling any fulfillment with my job. My coworkers annoy me. I don't understand my boss's mission at all. Is there a way I can make a rational decision about this and come to a solid conclusion about my future? Jobs can be tough to come by in this market and I don't want to make any rash decisions. Please help!