Take a sales job once in your career. What you'll learn will make you a better marketer.
Nothing bits being bitten by a customer who has no interest in your product, till you teach them otherwise of course.
You can easily tell those who've done it vs. those who didn't. one group is more real, more in touch with what the customer wants and how to get it to them. The other generally speaks in tool language (social marketing, campaign, ROI, blah, blah, blah.)
No matter what you believe marketing does: No sales, no business...no business, no marketing.
If you're not helping sales today, review what you're in the job for.