Persons with mental illness sometimes have more difficulty than others coping with the losses that occur periodically in everyone's lives. Losses can include a death, the end of a relationship, or even the end of a good job. Feelings of loss can occur from a relationship that never happened but that the person with mental illness hoped would happen. Everyone has a right to their feelings so long as it doesn't result in harm to others or to oneself.
I was very upset when my fifteen year old cat, named Boris, passed away. That cat adored me and we were buddies. We would sit together every day. I blamed myself for his death because I gave him Purina cat food, which was something I shouldn't have done. Self-blame apparently is normal.
I am in the process of dealing with the death of my father, which occurred a little over a month ago. If I were less stabilized, this loss would have resulted in a relapse of psychosis for me. I have delusional thoughts that my father died because of something I did. Yet I realize these thoughts are not rational.
Losses that occur in everyone's lives are particularly difficult for persons with mental illness, and can result in relapses unless the person is very much stabilized. I am lucky that I have sixteen years under my belt of no relapses, because I really looked up to my father, and I miss him a lot.
When a loss occurs in the life of a person with mental illness, they should take special care of their self, and they should get extra support from those in the support network that they should have.
Again, an end to a relationship, even one that wasn't mutual, can entail the experience of loss which is very real. Such a loss can even be harder because of the self-recrimination involved as well as the possible belief that one's feelings aren't justified.
How well or poorly someone copes with loss can be a litmus test for how well a person with mental illness is doing in life. However, there are no rules to the experience of grief.
Many people who ordinarily don't have a mental illness may experience a temporary mental breakdown when a spouse dies. I know of at least one person like this. The human organism experiences distress when someone close dies because family members have a strong connection that has biological ramifications. Losing a loved one is very much like losing a part of oneself because we are not the separate units that we appear to be.
Sometimes splitting up with a loved one can be so difficult as to resemble an emotional amputation. An end to a relationship can be nearly as hard to cope with as a death. It is something that people may automatically trivialize, but that pain is real, too. And if that pain goes unacknowledged or isn't dealt with, it can badly affect mental health.
When experiencing grief, it is important to "manage" the emotions so that one does not go too deep into the pain zone. You might equate this with repression. However, I believe it isn't good for a person to go too deeply into painful emotions, just as it is bad, on the other end of the spectrum, to not acknowledge these emotions.