I work really hard to stay in shape and eat right. Now I have a diagnosis of brucellosis. What else can I do so that it doesn't affect my overall health?

Be sure of dx. I am going to assume that the diagnosis has been made by a real culture and/or rising IgM titers, and not by a charlatan's phony laboratory (there are a few of these). City folk get brucellosis from "healthy unpasteurized" dairy products. Try to figure out how you got it and who else might be at risk.
Nothing. Your state of health and diet have little if anything to do with your diet unless you are ingesting unpasteurized dairy products. You get this from animal exposure through defects in your skin, inhaling aerosols of animal secretions or getting them into your eyes. Once successfully treated this should not adversely affect your overall health, assuming it is treated appropriately.
Get treatment. Brucellosis is a bacterial infection and can be treated with antibiotics. Do not try to treat it with exercise or other "natural" methods. Antibiotics are effective.