If you're experiencing it you can feel divorced from your own personal physicality by sensing your body sensations, feelings, emotions and behaviors as not belonging to you, and other weird shit like that. For example something i felt was the feeling of putting my hand through a table when i moved my hand towards it without looking; its just so hard to explain.
As i said before it can be a somewhat uncomfortable feeling and you might feel depressed or like your going crazy (like a lot of threads lately). Sufferers feel they have changed, and the world has become less real, vague, dreamlike, or lacking in significance. It can be a disturbing experience, since many feel that, indeed, they are living in a "dream". However it can also be a very good way to look inside yourself and actually find out who you are. You can reflect on life and the wolrd far easier due to this detachment from your ego, because you take a far more neutral perspective. It can manifest itself as partial or full ego loss, though the latter is much rarer.
Derealization is another dissociative symptom and can be caused by stress or underlying psychological/neurological disorders, hence why cannabis can bring it out in people. It is an alteration in the perception or experience of the external world so that it seems strange or unreal. Other symptoms include feeling as though one's environment is lacking in spontaneity, emotional colouring and depth. Essentially, your perception of the outside world is fucked up.
The detachment of realization can be described as an immaterial substance that separates a person from the outside world, such as a sensory fog, a pane of glass, or a veil. Individuals may complain that what they see lacks vividness and emotional colouring. Emotional response to visual recognition of loved ones may be significantly reduced. Feelings of deja vu are common. Familiar places may look alien, bizarre, and surreal.
Derealization is a subjective experience of unreality of the outside world, while depersonalization is unreality in one's sense of self.
Just keep in mind that you will get better, normally after a few days or a week. Make sure you drink and eat plenty. Don't look at the experience negatively, try to look deeper into yourself and refelect. You can change yourself and your life during these difficult periods.
Important: These are illnesses, as opposed to a "happy fun time lucky tripping balls!" time. (Thanks kG_Blazed)
Originally Posted by MoonCheese
What your experiencing is your mind straying away from your ego, or your "human personality"
Once must keep in mind that that your mind and consciousness is separate from your human outer personality.
You need to understand tat what youre experiencing is a good thing, people look for ways to feel the way you do.
In drug terms its called "loss of ego"
Many people who use shrooms, or other drugs that help you realize that your human idea of a reality is only imagination.
When you feel disembodied, or depersonalized, just take it in, and reflect.
Many great thoughts and realizations have been brought upon many other people, who know how to deal with this loss of ego.
Trust me, its a good thing if you understand it.'
If your fairly new to weed, its just the weed helping your mind realize that what you once thought of as "real" or "reality" isnt what it seemed to have been.