It would really depend on what's causing the emotions, so this can't be answered in a general way. Statements like "I have dealt with mental health myself" are dangerous. Just because you've dealt with one type of mental health issue doesn't mean that your experience generalizes to everyone else. For some people, going off meds can be truly disastrous. "Controlling your own emotions" is most definitely not always possible.

The distinction between environmental factors and "true" illness is not always that clear, because as some have described before me, people with clinical disorders such as bipolar are often much more sensitive to stress and other triggers than "normal" people. Even if an outside factor seems to be the trigger of a depression, for example, that doesn't mean there's not an underlying clinical condition that warrants treatment with medication.