Excellent advice from Ev Williams (Twitter, etc.), one of the most prolific and successful entrepreneurs of our time.
I can't say it better than this ... so I will just quote it in its entirety below:
1. Work with Amazing People
Don’t compromise on who you choose to found your company with and hire. Do not put up with ego-centric personalities or downer attitudes.
2. Take on Big Challenges
It’s pretty simple: Hard things are valuable; easy things are not so valuable. Reaching the mountaintop is rewarding because it is hard. If it was easy, everybody would do it.
3. Focus
Say no to most things: Features. People. Partnerships. “Coffees.” Projects. Only a few of them really matter. (Yes, it’s hard to know which.) Don’t get distracted.
4. Take Care of Yourself
When you don’t sleep, eat crap, don’t exercise, and are living off adrenaline for too long, your performance suffers. Your decisions suffer. Your company suffers.
5. Love those Close to You
Failure of your company is not failure in life. Failure in your relationships is.
Take heed young entrepreneurs ... he's absolutely right.