When i discovered what they do & who they are, I was set to write user stories. It is a humbling experience to claim that, say, Darren wants to keep track of his performance, to be honest. But studying the end user made me really understand what they feel, what they want, what they don't want (equally important!), etc. Moreover, by building a rapport with the end user, I knew I can come back to chat with him, be there a specific question I forgot to ask.