After someone has endured a low point on their own, their heart changes, becomes hardened.

They have seen the ugliness of human nature and experienced the realities of society. They know that during the lows, no one will come to your aid in your time of need; only when you succeed will everyone come to add to your achievements.
No one knows the helplessness and collapse they experienced during their low times, and no one really cares about that process.
When you're down and out, don't blame friends for not helping you, because they need to survive.
After success, don't forgive easily, because you also need to survive.