I don't think I'll ever help an elderly stranger again, can I be frank with you on that?
Why do you want to stop helping elderly strangers? Is this for your own satisfaction you came up with that?
Because I'm a bitter son of a bitch.
We can all feel bitter sometimes, but don't let it be a way of life for you. Helping the elderly is important, because they're vulnerable members of society. Treat people well now while you're young, and people will be more inclined to take care of you when you're old and vulnerable.
I don't really care.
You should seek some therapy to get rid of the bitterness you feel inside. Did something happen to you to make you so bitter? The therapist will help you sort those things out so you can be a moral person like everyone else.