You lose your sense of self. The boundaries between "you" and "the world" fall away and you feel deep connection with everything around you. It's a main feature of psychedelics, and at any dose it is where the "one with the universe" feeling people describe comes from. "Ego death" happens at high enough doses where you *truly* lose the concept of "me" and cannot access your rational mind that knows you are an individual human and all that. You experience "oneness" in a very real and authentic way, and that can be extremely difficult and disturbing for some people depending on how it manifests for them in their trip. It can also be a profoundly beautiful experience that alters you for the better.

This is why setting up your trip is so important for success if you intend to take a larger dose, and your mental state/unresolved issues/whatever can surface in very extreme ways during this if you have not been caring for them or considering them when entering the trip. The OP's description of a trip that kept coming back to themes of suicide, and ultimately ended with a fixation on suicide while losing most knowledge of himself is exactly what I would expect here. It is a really good example of how someone who is dealing with depression should be extremely cautious about self-medicating with psychedelics. I don't know that OP or their GF is depressed, but it sure sounds like one or both of them might be. There's so much out there about LSD/shrooms/MDMA curing depression, but people don't realize those studies that have shown promising results are all done in a highly controlled manner guided by mental health professionals. Taking random shrooms with your buddies or partner or whatever is not the same thing.

Sorry, that turned into a rant...