I want to change the world.
Blasterous, Instagram, Outright
The most frustrating would have to be the challenge of not being able to move as fast as we'd like. The most rewarding would have to be daily sign-ups and returning users. There is nothing as validating or rewarding as people using your product.
We make many mistakes and depending on the situation any one of those mistakes could be the N0. 1. I would have to say a consistently bad mistake is failure to look at your service from the perspective of your target users, who have no vested interest in its success. Do you have a product or service people need? Are you solving a problem? Be humble, receptive and never drink your own cool-aid.
1.) Finding the right team is job one. Without the right people, you are sunk.
2.) Perseverance pays off. Most over night successes took years.
3.) Have fun, stay positive and in love what you are doing. Entrepreneurship is a challenge and extremely taxing on all things (personal as well as professional), so do your best to enjoy the experience.