What's the #1 thing an entrepreneur be spending his time on?

Out of all the different tasks founders have to do, what one thing do you think is the most critical of them all?

Love your idea, but don't be married to it. Validation from your customers coupled with their ability to pay will determine if you idea can blossom into a sustainable business.

Understand general rules and advice on entrepreneurship and startups, but adjust them for yourself and for your business. Blindly following cookie-cutter advice from every blogger and expert only leads to confusion.

Some common rules and my view on them:

If your MVP has no traction doesn't mean your idea is bad, could be execution or value proposition - pivot until you get it right or run out of pivots to try.

Freemium isn't dead, it's just not for everyone. Most B2B products stay away from freemium, but it's a reasonable option for getting your product into the hands of as many consumers as possible early on. You need to maximize learning and you can't do it with 10-50 paid customers.

Profitability from day 1 is great, but not at the expense of growth and losing market share to competitors. Profitability is practical and safe, but as long as you are not spending borrowed money it's Ok to sacrifice profit margins for faster growth if that's what you prefer (get bigger faster).

TYPICAL startup becomes successful in 1-2 years. Guess what? It's Ok if it takes 3, 4, 5 years. Watch this amazing video about Constant Contact growth path - http://businessofsoftware.org/2013/02/gail-goodman-constant-contact-how-to-negotiate-the-long-slow-saas-ramp-of-death/

TLDR: There is no simple rule or #1 advice for any entrepreneur/founder, the answer to any question starts with "It depends...". Learn to apply advice to your unique situation. There are so many factors - type of business, industry, business model, individual skills, etc. etc.