I think “checking yourself for lousiness” is a wrong approach in this case. When you try to help someone you should concentrate on your action, rather than on intellectualizing the moral value of your deed.

It’s very simple – if you feel like giving – give as much as you feel without turning on the feedback loop.

If you feel you can give ten dollars without negotiating with your internal Bible, then give ten dollars and forget about it. If it’s only ten cents than give ten cents.