I just launched my project officially and it's generating some revenue for quite some time now (small amount though). I first started working on it 2.5 - 3 years ago, but it wasn't full time, it was always a side project.

It's only me on the project, the whole time.

I don't really have an advice, just work on it and don't give up, as long as you don't give up, you haven't failed.

I wish you a good luck and a lot of persistence!