Your mission matters to you. There is no doubt about that or you would not be dedicating yourself to work on it. That is part of what makes the Nonprofit world so unique and inspiring - professionals are working on what they believe in, often sacrificing to do so, for something greater than themselves.
But! (There is always a but!) Missions take money. So you fundraise. You network. You connect. You share. You ASK people to get behind your cause with their resources.