How to stand the grief?

I have just turned 51 and find the middle of the worst nightmare: facing divorce when I madly love my wife and two children (boy 7 and girl 4). I cannot stop thinking about what could I have done or not done how could I have been a better husband and so on. My life has become unbearable since I have being slowly going down to this point during the last 7 years, I think is no ones fault but again, I suffer each second of my miserable life and can only think of the horror of living the next minutes. The only thing I can stand for is for my kids. What can I do to bear this pain?