Tomorrow I am turning 50. I don’t normally write about birthdays but in my work with entrepreneurs I often tell them that a big milestone, such as raising a new round of financing, is a good time for reflection. My 50th feels like such a milestone. Not a day goes by that I don’t feel extraordinarily lucky and thankful. Other than a few nits, I am healthy. I get to work with wonderful partners, the terrific team at USV and an incredible group of entrepreneurs doing something that I love. I hav...