Keep trying - and one day you'll succeed
Yes, sometimes it really is a good idea and quit doing what you're doing in order to give preference to new things, things with more potential. But if you are working with something you are enthusiastic about, but just haven't been able to succeed with it yet - just keep trying.
But while you "keep trying", don't forget to pay attention to the things you do. Remember what didn't work. And then try the same thing, but differently; or try doing something totally different in order to get your business out there. If nothing what you do works, then eventually, you are bound to find something that does.
It's all easier said than done, I'm aware of it. But if you don't even try...well, we all know the results in this case. Only by doing nothing or in case of quitting can you be sure of the results...which of course is a failure.