Nowadays, you can read all existing material about marketing, retailing and sales; you can even collect and store those books and videos until they can sink a cruise ship with their weight; but it would be worth nothing if you just leave the most important factor out of the equation.
People are the bases of all interaction. Whether you call it sales, marketing, business, politics, or whatever, all that is, is human interaction. If you miss out on the bases here, you will miss out there for sure.