What is he thinking?

So, alot has gone on lately. Probably more than I can deal with. I just wish someone could explain to me what goes on inside a man's head? How can a grown man (well, maybe not all the way grown, but 23 yrs old), turn his back on his family? How can he turn himself away from his 3 year old daughter, while some nights she is crying for him? How does a mother stay strong, while she's hurting inside? Those are just some questions I have, and wish I could find the answer to them.