When asked, people provide different answers to why they participate in Open Source projects. The same way, to succeed in Open Source can mean many different things.
Get paid to work on Open Source. Get friends all over the world. Learn new languages and technologies. Teach others. Solve difficult problem. Work together with others. Improve the world. Work on free software.
Personally, I think a primary motivator to participate in Open Source is because it is fun and rewarding. If it is not fun and rewarding, then why do it? And if it is fun and rewarding, is that not enough?
No matter how you decide to measure if you reach "success" or not in your project, an important factor is "when".
I will continue to maintain that one of the primary virtues in development, Open Source and elsewhere, is persistence. Do not stop. Do not give up. A quote that has been attributed many different historic figures goes like this: "You never fail until you stop trying." and the same goes for success. As long as you keep at it, success is still possible on the horizon. However you decide to measure it.