Selfishness and self centeredness seem to be our problem. When I am thinking of only myself,( what i want, the way i think things should be) pain will surely follow. Weather it is guilt, anger, lonliness or some other negative feeling. When i have a service minded attitude, thinking of what I can do to be helpful, do i get relief from my own head.
Feelings of guilt can be part of depression or the depressive aspect of bipolar. That's common and I have experienced it myself. For me the best solution is to find a practical activity that I can focus on or a hobby that I can enjoy. Before I acquired my physical disability at any time that I felt down I would go out and see people at some occasion. Regardless now I still keep up with recovery and engaging with people at times when things feel down. I got into volunteer work that led to advocacy to begin with as helping other people was one way to accomplish this. Everyone has their own way to achieve this though.