It's hard to stay motivated when people, who are impossible to please, ask for help. Given they're going to be displeased regardless of what you do, it's tempting to not even bother complying with their requests. But unfortunately, that's often political suicide. So, just do the bare minimum to make it clear that you understood the request; there's no need to put forward your best work because it'll likely go unnoticed.
But, that's a short-term solution. If the opportunity arises, you should get these people out of your life. They don't deserve your respect. Blatantly wasting other people's time is the worst egocentric offence.
When asking others for help, remember what it's like to be on the other side. Be flexible with what people come up with, especially if you don't have a clear idea of what you want / need.