Nothing left but anger and frustration

Old mean and ornery people were once filled with love, though it's hard to believe. Everyone was born with the same outlook, it's just people ruin other people. In return those people change and lose those people who once were a source of love and friendship. When you have nothing left you either give up or use the anger and frustration to fill and fuel yourself, to a point where that's all there is eventually. Some people feel no love anymore for that reason.