You are rarely in a conversation, certainly a professional conversation, where at least one of the participants isn't selling. You can be with the same person, or persons, in subsequent conversations, when the one who is doing the selling changes, but someone will be. The very life force of survival instinct, implies a measure of control, and in business, if not in all human interaction, either force, leverage or salesmanship are at play to ensure survival.
The next time you are with your boss, pay attention to who's doing the selling, you or your boss. Either you will be selling him on your efforts, desire to improve or results, or he will be selling you on the esteem in which he holds you, or what you'll need to do to earn it, or why you should be supportive of him (maybe even to vocalize that support)--or perhaps, even what you'll need to do to keep your job. In virtually all business conversations, at least one of the parties will have an overt agenda and the other, at the least, a covert one.
The very uncommon, and therefore exceptional person (boss or employee, buyer or seller) is much less focused on his own survival than he is on the quality of his time spent. These rare birds tend to look for seed to feed others and trust there will be enough left over for them. They enjoy a special sense of personal value and fulfillment in seeing those with whom they spend time be better off for the contact. If you've worked for someone skilled, and who behaved like that, there was little you didn't try to do to justify his interest in your growth and well being. You were better off and better at the job, for the contact. If you've ever spent time with a "seller" who knew what he was talking about and subjugated his interests to the success of your endeavor, you prayed that he didn't retire before you.
If so many of our professional relationships are connected by complementing or differing agendas, and we each try to make the most of those relationships by furthering our own agendas, shouldn't we do what we can to get better and better at it? Shouldn't we get better at selling?
Rhetoric aside, the first step toward that end, I would assert, is a worthwhile agenda that speaks volumes about your mission and character. Who are you and what do you stand for? What do you value? Why would I want to spent time---or money---with you?
Love Your Work and Work Tirelessly
Communicate Honestly and Fearlessly
Serve, Don't Sell