With experience in meditation you will start gaining a better understanding of what you are. You will learn that you are consciousness, i.e. a conglomerate of sensations and thoughts. You are not your self. Your self is a tool to interact with the world. In the isolation of meditation, the self reveals itself as useless. That’s where you can see clearly that it is only tool. Just like the mind that contains it, the default state of the self is silence. It is only when you interact with the world that your self is useful. 

Your self determines your tastes, your values, your memories everything you would categorize as your identity. We build it life experience after life experience. It becomes so big and it seem so important to us that it makes us see ourselves as separate from the rest of the world. The self is created by the mind to make sense of the view point that we are. Enlightenment is seeing it with your own eyes. Being everything and everything being you is what it means to unify with the divine. The beauty of entheogen is they give you a glimpse of it.

One of the most idiosyncratic traits of psychedelics is the dissolving of the ego, what is commonly called the breakthrough. Psychedelics shut down or dim down the part of your brain (the prefrontal cortex) responsible for creating and maintaining your sense of self. Entheogens have the capacity to give you a breakthrough at a certain dose. It can be scary for some. To prepare yourself for the breakthrough experience, I would recommend studying the self and more importantly, practicing insight meditation so you can see it first hand. It will help explain it. 

Some people refer to the breakthrough as the feeling that you are dying. You only feel that way if you are convinced you are your self or your ego. Some people describe the breakthrough as the feeling of being everything. The self is what gives you the impression of separation between you and the rest of the world. Shut down the self and you literally pour into the Everything. The last benefit of insight meditation I would like to mention is that the realization that everything is sensation can help you deal with the most bizarre and sometimes scary sensations an entheogen can make you confront. If you find yourself in a difficult situation during a ritual, remember that this is only a sensation and sensations come and go. They are source of dissatisfaction, but only if we let ourselves be attached to them. They are not experienced by a self. This is not you. You are only the witness of it.