Definitely anxiety, stress, and related frustrations can trigger strong reactions from me, at times. Hormonal fluctuations, like fern mentioned, definitely can, too. I've dealt with these things (save the hormonal) since childhood, and some of it is nature and some nurture.

Low stress lifestyle has done wonders for me and my bipolar disorder, but doesn't keep episodes away completely. But it, with various coping skills, calms them, anxiety, and anger outbursts quickly.