I started a company just because I wanted to. It took me 6 years to realize I didn’t have a direction on the ongoing path.
A mission is important. As Stephen Covey said in the 7 habits of Highly Effective People, to “start with the end in mind”. A mission, an end goal could help driving down the path. That gives the meaning to continue no matter profitability or user acquisition. The motivation won’t be distracted by external factors.
What I do nowadays is just to build something I would use personally, an app that I use daily, a Medium blog that keeps what I learnt along the way, a sharing that benefits my friends. Gradually I am helping the people around me. This may not be huge, but as like Airbnb, Facebook and Whatsapp. They don’t know until after a few years.