There is many views about heredity on the subject of mental illness.
Take for instance, Heredity and Alcholism.
Some people feel it's passed on through genes, some may say it's a matter of the individual taking control of their life.
I don't think bipolar is passed on though, but that's just me. We all have different moods from day to day. Trying to be happy in a stressed world is hard for even a stable person.
When I feel guilt ridden or overwhelmed, prayer helps bring me back to reality.