My college marketing professor/advisor had a slogan that he pounded into our heads during my last semester of college: "Build successful relationships, and profitable transactions will follow." This can translate to anything really...it doesn't have to be a monetary "profitable transaction".
In my career, I've really taken this into account in all of my daily work. I'm constantly striving to develop a better relationship with clients, vendors, co-workers, etc. You never know when you might need to call out a favor, and have someone willing to come to your rescue. Not all relationships turn out great, but if you work at it, most of them can.
To give you an example, I have developed an amazing relationship with one of my clients. We are able to be very up front with each other, which often times leads to more productive conversations and work. She also trusts me enough that I can do things like ignore her questions when there is a crisis happening at an event. She knows it will be handled, and that she will get details later. This relationship has allowed us to produce some great work together. She has been impressed enough by our work to give us exceptional recommendations to other potential clients.
