It's humbling to feel helpless in the face of deep suffering. We just don't have enough money, enough fortitude, enough influence, or maybe enough compassion to do what it takes. Encountering an African slum, it sounds like "my crumb of bread to feed this mountain of need... what was I thinking?" Shame and guilt are eager to remind us how much of your life and money we have spent on personal comfort and self interests. Resulting hopelessness or cynicism can cause us to stop giving, or caring, or both.