The High Priestess is usually shown sitting between two pillars, in a portal between worlds. If you internalize her wisdom, you move from one world into another. On a more mundane level, so it is with the Twos. They show a time of balance or limbo, before a choice is made (or in the case of the Cups, just as the choice is being made). At the time of the Twos, there are two possible futures and choice to be made. Once the choice is made, then one of the possible futures is eliminated. With the High Priestess, once you admit that knowledge, whatever it is, that lies within you, you are initiated into another world. The old one is gone and you can never go back to it as you will never be the