How do you stay motivated working on your projects?

I’m working in two side projects that are very useful for myself and I use them both for other projects I have.

I don’t have an audience for these new projects, don’t even know how I’m going to market them and to whom. Whenever I’m working on them I get so frustrated and demotivated because I don’t know if they are going to be useful and because there are better bigger competitors out there.

How do you fight these feelings?