The best route for you is to spearhead it yourself and make another go of it - but it's assumed from the tone and wording in your posting that you're not in this frame of mind...

Suggestion: don't let go of something with promise! Look to partner with someone who's expertise matches well, but keep a significant stake in the company. Look to create a vesting agreement with a potential partner that has a 1 year cliff with bonuses for performance. (Talk to a legal expert!)

My point is that rather than selling it off, you could 'pay' someone in shares for performance-based work. They would end up with n% of the company after m years plus p% bonus. They would have you as an advisor/co-founder resource.

There should also be buyout provisions should either of you want to take on the company full time again, perhaps.