My general rule of thumb is to try to be as pleasant (or more) than I want to be treated. It really takes no additional time. That's what should usually happen, but...

Unless an agent is being purposefully obstructive in assisting me, speaks in a universally inarguable tone of rudeness or something similar, I have come to accept that these are human beings who have a shift that is irrespective of whatever may be occurring in their personal life.

Suppose she learned on her way to work that her husband is having an affair? What if a close family member or loved one has been hospitalized and she needs to be there, but can't? These are just two of many examples what can understandably make it difficult to impossible to put on a "happy face."

Ideally, there would be a means of accommodating the personal events in the lives of their employees, but they may need every available staff member on board that day for innumerable reasons. I try to cut them a lot of slack unless they use it as an excuse to try to make my life equally miserable.

It's disappointing to have an agent unwilling to help resolve an issue, and there are days when - as a human myself - i may have something I simply can't emotionally override. Still, it's unlikely that the two of us would cross paths at the same time.

Edit: My views posted here are not intended to be critical of the OP in any way. Just offering a perspective that makes MY life easier and less stressful. Traveling has enough inconveniences that are consistently part of the process.