What if you could make other ideas work but stay focused on the challenging one?

Why don't you spend a few hours a week in one of them, as a side project? It would be harmless to check how it goes and how you feel.

Muse businesses are good. If you're sure they're a solid bet and they have a clear business model that can make money, I'd say give 'em a go.

If they're not of the "simple, direct route to profit" variety, though, concentrate on the main biz. Do what you're excited about.