> Could depression, or other mental illnesses, be the outcome of one's bad decisions (or failure to make decisions)?
Sometimes, the outcome of one's decisions (bad is an unnecessary value statement here. Was it a "bad" idea to start a restaurant that failed and made you sad? Cmon).
However, a huge swath of mental illness, including depression, is the result of environmental and genetic factors utterly outside your control. Your mom smoked crack when you were in her womb and somehow that's "the outcome of your bad decision?"
If you have an emotionally abusive partner, and don't do something about it, perhaps depression is acting as a prompt for you to take action. Some part of you (your soul, say) knows better, and via pain (depression) is trying to shift you towards a better, more joyful, result. I believe we have an innate guiding system, and that this is how it works - move away from pain, towards joy.
You can fail to take action, you can take drugs to manage the negative situation more comfortably, but, if abuse is the underlying issue, a genuine change of circumstances is required.
It is important to listen to your body and mind, and for sure - make changes when things are bad. Staying with abusive partners is not worth it.
However it can take a while to realize the problems and manage to get out. This may have effects that last for a good while.
People do not deserve abuse or the negative effects of such abuse, just because they technically could have made a change, or made it earlier.