There are many triggers or causes of bipolar disorder and some of them you might not even think of. Your doctor should be able to help in getting a list of factors that can trigger the condition.
If you are manic-depressive and married, you can unwittingly bring a rift between your and your spouse. Unfortunately, this can also trigger off the mother of all depressions in you. It is not a secret at this time, but a marital failure is one of the most potent triggers of bipolar disorder known to man.
You may want to keep an eye on the amount of work-related stress you allow into your life. It is inevitable that you will have some emotional investment in what you do, but because it can trigger a manic episode, or even a depressive one when you suffer from bipolar disorder, you have to at least control it. Promise me you'll try, at least.
People with a genetic vulnerability to bipolar disorder are often the ones most affected by the triggers of the condition. Other kinds of patients are susceptible too, but not quite as badly, and so you have to pay special attention to what factors you expose yourself to when you suffer from this condition.
Every woman who has kids goes through the prenatal development phase of life. When they also suffer from bipolar disorder, they may slip into either mania or depression when they get to that point of their lives, and they may not 'slip' out of it in a hurry. Such a trigger is inevitable, though, but you can take medication to control it.