Frustrations

Why is it that no matter what you do to make things work, there is always someone or even a bunch of people to make it hard on you. If people really want to participate in things they need to prioritize. You can't do everything! It took me 10 years to figure that out. But the people who are the most willing to participate are the ones who are in everything. So what do you do? Its always a catch, I either cancel it or work around people's schedules. I know I can't get everyone, but you need people to get things done. The question is what to do?