a leopard never changes its' spots

As much as I'd want to believe that people do realize their mistakes and repent, most of the times they actually don't. As the saying goes, a leopard can't change its' spots. So I realize I am making a mistake yet again to trust this kind of people. Not anymore.

And to someone I love, quitting is sometimes winning. Sometimes, an obsession with never quitting is worse than quitting itself. When costs outweigh benefits, we abandon the plan/project.