It's surprising to see a person who has rubbed shoulders with the best (At Google and UWash) still feeling nervous before a demo. Could you elaborate on that ?
Yep. There was a lot on the line and the chances were quite uncertain -- Y Combinator takes, perhaps, 2% of applicants. I've seen them say no to more than a few smart all-Google teams (or all-MIT teams, all-Stanford teams, etc.).
Agreed, there is a lot of sports psychology related stuff written about how sportsmen use nervousness to motivate themselves. How do you not show you are nervous ? Because that is not a good signal is it ? I get nervous for interviews I've prepared decently well for. I don't get nervous when I'm either fully prepared or not prepared at all.
As a former gymnast and YC founder, I have some experience with nerves. The best advice is to prepare as hard as you can, and then relax, knowing that you've already done everything you can to succeed.
Obviously, practicing being put on the spot is also valuable - find ways to do things where you have to deliver even while nervous.
Ex-Googler here. Working at Google is very different than making a presentation representing your own idea. At a big company, assuming a collaborative culture, your teammates are rooting for you to do well and you don't go into a meeting expecting that to be the last word if they don't like your idea. OP had already quit his job, staked his reputation/ego on his demo, and had to speak for himself in a tough room, so I think it's reasonable to feel some level of nervousness.
