Probably flexibility (see how neatly I got around having to choose just one quality?). Within organizations, product managers often have to engage with users, team members, stakeholders, and partners. They have to understand the business needs and the customer needs. They need to effectively make use of both qualitative and quantitative data. And then they need to take all of this and make good decisions, often very quickly and almost always with incomplete information.
Airbnb, Whatsapp, Facebook: it took each of them time to realize how big each of their ideas truly were. What kept them going? Determination, sure. But also small nudges from others. In my own search, it was startling to me how one coffee or a casual word from a friend could turn my day up or down. I think that’s one of the things that makes Silicon Valley work so well: fewer haters.