The lesson is: If you find yourself repeatedly in situations where people ask you to do something for them, but at the end they don't seem to appreciate what you did for them, or don't even care about the thing they asked you to do... and yet you find it difficult to say "no"... ask them to contribute to the project first.

This will help you get rid of the projects they don't care about (including the ones they think they care about in far mode, but do not care about enough to actually work on them in near mode) without being the one who refuses cooperation. Also, the act of asking the other person to contribute, after being asked to do something for them, mitigates the status loss inherent in working for them.

My personal experience confirms this! One of the benefits of being transparent.