The passion would be to help customers succeed. Or at least it should be.
The frustration mostly has to do with the clients reluctance to change!
Great answer by Oliver. What I love most is being out and meeting people. Every new encounter is exciting.
What salespeople find most frustrating is what I call, "chasing rainbows". It's the idea that if I sell $100k this year, I will be expected to sell $450k next year. Sales goals always increase, but not necessarily the support.
Building loyalty with clients and creating a situation where you become their trusted advisor takes time, but I believe is the ultimate for a sales professional. Not only does it make you feel like you've accomplished something, it moves you up in the tax bracket.