Because I'm still organizing my thoughts as I'm writing this. But what started this was watching episode 14 of Season 1 ("Nightmare"). It's a cool episode, and when I first saw it, I didn't think much of it except that it is entertaining. But it has a deeper meaning; In this episode, there are two adult men who experienced the same key event in their infancy. Their moms were killed by a demon in a horrible way. After this event, the dads of the two kids coped with it in an entirely different way.
Both families were loving and normal prior to the event. But Sam's dad and the other kid's dad dealt with murder of their wives in two different ways.
Sam's dad remained loving of his kids, but he became militantly protective and started raising them in a strict but loving atmosphere, teaching them skills they need to survive and becoming a demon hunter in an attempt to get vengeance on the thing that killed his wife.
The other dad became bitter and blamed everything on his son. He physically abused his son throughout his childhood and adolescence.
The episode makes you look at people's life through a kind of a special prism, a prism that can reflect alternative lives had a critical event never took place.
Seeing how Sam's family was like before the murder, you get a clear sense that had the murder not happen, Sam would have grown up to be a completely normal kid, instead of the more soldier-like psychology he has grown into.
The kid from the other family could have also grown up to be normal, but instead he grew up to be a hateful, insecure and violent adult. The way the two dads coped with the situation made a huge difference in who their sons grew up to be.
But I guess what I found most interesting about it was how a seemingly completely normal person, faced with unusual circumstances, can change themselves to be a warrior, not just skill-wise but also psychologically; that they have it in them all the time, but that life often leaves some personality traits dormant. But a person with a seemingly normal life and sweet temper, can change to be tough, resilient, persistent, accustomed to dealing with difficulties and not letting those difficulties stop them.
And lastly, I realized, the character of the Winchester's dad in the show is a great man. A man that stayed loving in the face of a terrible event and at the same time became active about it rather than just accept it as a "weird accident".
The same episode shows another moment, where he talks to his son, Sam, and tells him that when Sam was born, one of the things he did was p[en a savings account for Sam's college, for when he grows up. And he said it with such joy and love. The ability to love someone else like that is one of the most important things in life. I don't know if that, by itself, is the deepest joy, but I think that someone who can get so much happiness from giving to someone else at least has the capacity to be very happy. When we lose the capacity to love we also lose the capacity to be happy.