A personal belief is that if you're not personally invested in what you're working on, you'll fail.
Embrace your constraints.
Creativity is an infinitely renewable resource - you are not going to run out of it - so don't be afraid to use it.
Willingness to take risks is the path to success.
Creativity is a renewable resource.
At Twitter, mobile is in our DNA ... For us, it's all about mobile, and it always has been.