I was a successful retail and enterprise salesperson earlier in my career. I also suffer from lifelong depression.

I did not fake "happy happy joy joy," but I also did not allow self absorption to inject my mood into my business. My model is that sales is a career that involves having structured communications.

That was a lifesaver for me when feeling depressed, because I could focus on the structure of what needed to be accomplished rather than the unstructured touchy-feely business of "getting along with people."

I suggest that "YMMV." Salespeople are not all the same, and some break preconceptions and stereotypes hard while being successful at what they do.