My father used to and still yell at us whenever we do something wrong, mostly on super mere mistakes. Yet I can't deny he buys us all we want and often treats us well.
My parents got divorced when I was 12, and of course it was very stressful. Both of them put the blame on the other, tried to brainwash us to hate the other. I was confused, my brother wasn't really affected as he chose my father's side since day one.
I have a year-younger brother. We used to get along pretty well, however, in the past few years I became more and more isolated. We still have a good relationship but it's just not as before.
My father remarried days later, a mother of 3, one of them was handicapped. She bore my younger brother too. When my mother remarried a year later, I had to move and live with my father, which destroyed me more than their divorce. My father kept telling me your mother doesn't love you, she chose her life over you. I didn't believe him, simply those words broke me. Anyway, my both parents got divorced from their new partners.

I think the main reason behind my cold-heartedness is that I built a wall around myself through being apathetic. The amount of pain I went through at young age -mainly from people I loved- forced me to hate the fact I love them and even felt at the fist place, thus I gradually stop feeling any emotions as the years passed. It was unintentional though, I created this assumption looking back at my childhood. I guess my brain decided to disable the "feel" button either because it had hurt me or so that I wouldn't feel hurt at all.

P.S.: I realized you were asking about Bipolar when I got to the last question -I didn't know BP stood for bipolar- *laughs at herself*