Sesily's recent post about triggers inspired this one. Rank your top triggers (top 3, 5, 10, however many) by how likely they are to effect you.

Some possibilities:

Lack of sleep/interrupted sleep pattern
Interrupted daily routine
Travel
Stress/anxiety
Major life changes (new house, pregnancy, marriage, etc)
Personal conflict/arguments
Goal pursuit
Social stimulation (friends, opposite sex, etc)
Seasonal changes
Hormonal changes
Alcohol/drugs
And so on....