Things don't happen according to plan very often, so you really need some flexibility when it comes down to dealing with people and understanding them better. It's very important to be open-minded. If you're unwilling to learn from other people, then there are going to be a lot of things in life that you won't achieve or experience because of your own stubbornness and unwillingness to admit that you might have been wrong about something. When it comes down to being flexible and having a big picture perspective, we all can do a better job at trying to understand where other people are coming from and what they want out of life as well.
As humans, we make assumptions about how other people see us all the time. These assumptions go both ways, though, meaning that sometimes we assume the worst from other people while they might think the best of us. Jeff Lerner strongly encourages us to be as open-minded as possible and not just label people as being good or bad. If you're working with someone on a project, then it's probably a good idea to actually listen to what they have to say instead of assuming that you know better about the subject matter because you might actually learn something new.