Why was british general burgoyne overconfident about his army's abilities while he marched on albany new york

He believed that the army that he had was vastly superior in all aspects, both in number and in skill. He believed the local rebels to be a small army consisting of poorly educated layman in the arts of war and believed that his professionally trained army of almost 6000 soldiers would easily defeat them, however he was easily beaten in what became one of the most important battles in the war's history.