When someone does you wrong, do not judge things as he interprets them or would like you to interpret them. Just see them as they are, in plain truth.
So much anguish and anxiety we experience is simply in our heads. Furthermore, people know this and depend on the fact that they can get into other peoples' heads! But the key here is that we have to let other people into our heads for them to have sway over us. And knowing that we can let other people into our heads, we also know we can just as quickly kick them out.
Our mind is a citadel and we have complete control over what comes in and tells us what to do and what to think.
To have discipline of assent, the first step is to simply break things down. Marcus does this over and over again in his Meditations.
What does breaking things down mean? It means making "a definition or sketch of what presents itself to your mind, so you can see its essential nature and identify it clearly, in whole and in all its parts, and can tell yourself its proper name and the names of those elements of which it is compounded and into which it will be dissolved" (Book 3:11).
You can immediately do this with the most alluring of objects in your life now: seeking fame, consumerism, sex, money, power, perfect health. All objects and ideas that fall in these categories or virtually anything that is out of our control that we think could make us happy.
Breaking these things down is the process of taking the glamour and prestige and knocking it down. A diamond ring is just a piece of compressed carbon. Fame is just the clapping of hands and mouths. Money is just paper.
Break the allure.