Commentary on Meditations: B6:13

How good it is, when you have roast meat or suchlike foods before you, to impress on your mind that this is the dead body of a fish, this the dead body of a bird or pig; and again, that the Falernian wine is the mere juice of grapes, and your purple-edged robe simply the hair of a sheep soaked in shell-fish blood! And in sexual intercourse that it is no more than the friction of a membrane and a spurt of mucus ejected. How good these perceptions are at getting to the heart of the real thing and
penetrating through it, so you can see it for what it is! This should be your practice throughout all your life: when things have such a plausible appearance, show them naked, see their shoddiness, strip away their own boastful account of themselves. Vanity is the greatest seducer of reason: when you are most convinced that your work is important, that is when you are most under its spell. See, for example, what Crates says even about Xenocrates.

Anxiety and stress, fear, ecstatic joy, haughtiness, feeling superior - all of these feelings come from within our head.  All the science of marketing aims for is to hit one of these strings in our brain, which then we allow ourselves to be seduced by the sales marketer to give into that feeling and try to rectify it (usually through spending money).

The things that impressed people in Marcus' days were delicious meat, wine, a robe with the color purple in it, sex - all of these things were tied to his power and fame as emperor of Rome.  Interestingly enough, those same things are marketed today and show up as advertisements all over the Internet, billboards and TV.  We can easily assent to these ideas that eating delicious meat, wearing expensive clothes, making love will bring us fulfillment (make us feel better about ourselves, puff up our vanity).  But in the end, all they do is make us lose our reason and focus on things that are truly important (virtue - discipline, courage, justice, wisdom).

To not be seduced by these things, we exercise the discipline of assent.  We look at the physical characteristics and view them as they are.  A tender steak is nothing more than a dead cow.  The color purple is dye applied to cloth.  Wine is made from dead grapes.  Sex is skin rubbing on skin and a shot of chemicals in your brain.  Don't let these things make you lose your reasoning.  See them for what they are.  "Vanity is the greatest seducer of reason!"  In this age of "selfies", Marcus' wisdom is needed more than ever.

(see also Citadel p. 104-105, 165)