Mark Zuckerberg : Don’t set out to build a company, start with the problem that you’re trying to solve in the world.
The best companies that get built are things that are trying to drive some kind of social change, even if it’s just local in one place.
You have to pinpoint exactly what you want to do above anything else.
People decide often that they want to start a company before they decide what they want to do.
And that feels really backwards to me.
And don’t just identify any problem to solve — pick something you truly feel passionate about.
For anyone who’s had the experience of actually building a company, you know that you go through some really hard things along the way, and I think part of what gets you through that is believing in what you’re doing and knowing that what you’re doing is really delivering a lot of value for people.
And that’s how the best companies end up getting made.

Mark Zuckerberg was able to reject famous Yahoo’s one billion dollars offer to buy facebook in 2006. At the time facebook was around 2 years old with 20 million dollars revenue. facebook was only able to connect 9million people and according to Zuckerberg they didn’t see it go beyond that.
It was a turning point in the company.  
Those he worked with suggested that he sells the company but Zuckerberg  turned down the offer. According to him his whole management team left after that and they told him that he’d regret his decision.
But today facebook has over one billion users, facebook is worth approximately 500 billion dollars and Mark Zuckerberg is 5th richest man in the world.
His mission was different from money. He wanted to connect the world. A mission that has no price tag.

I hope you learned something. Cheers.