You can’t always tell if the path you’re walking—metaphorically, as usual—is productive or even really going somewhere. But sometimes it’s clearer. Ironically, the paths that get darker are often dead ends, you should be seeing some light approaching.
I’m not against the white light on the road to Damascus, or lightning strikes of epiphany, but they just don’t happen very often and not to very many of us. Most of the time, your creative journey is downright confusing and hard to see. It’s usually hardest to see at the beginning, though. If things are getting murkier, harder to interpret (for you, forget about explaining your work to others for this), or circular, it’s probably time to abandon it.
It seems counter-intuitive, because we’re often told we should stick it out in life. Successful people talk about the hard work that got them where they are, and how only losers quit. But you’ll know most of the time whether the road you’re on is getting you somewhere. You’ll be able to see, feel, and/or hear it. It’s not necessarily that things should be becoming easier. Just about everything worthwhile takes a lot of effort. But there are very few artistic gems that sparkle suddenly from a confusing and muddy place.
Don’t be afraid to start again. That’s your secret weapon as an artist: you can jump off the current path to a new one any time you want. You try things with as little fear as you can muster, but similarly you should feel free to walk a new road when you hit a dead end.