Within the refuge of your Inner Citadel, you are completely yourself. No one can tell you what to think or how to act. When you realize that the true, unique version of "you" lives in a mental fortress, you become free to act and reason. No longer are you pulled this way and that by external events and people. The only way to get to this realization is to constantly apply the discipline of assent. The is a matter of creating gaps between your mental fortress and external events - constantly. By this continuous exercise, all passions and events "lose power" over you (or perhaps better said, you realize that you were granting these things too much power in your mind). And furthermore, once you've realized you have a mental fortress, you are free to apply reasoned and deliberate judgement of everything. And furthermore, if you focus on attaining virtue, you are on your way to wisdom.
(see also Citadel p. 120, 122 [read that entire page])