A major reason for my depressions where my fathers early death, which i hadn't really processed up to that point. In my first ever trip, some hours in i fell into a state where all that sadness and regret just overpowered my conscience, quite literally myself. Yet at the same time i was calmly observing myself, and i was able to reflect quite deeply onto my emotional state, ironically all whilst beeing utterly unable to control it.
This "loss of ego", i could maybe describe it as an "out of body experience" made it incredibly obvious to me how to put my regular emotional state into context and understanding how rejecting the process of grief and feeding my fears of loss had created the state i was living in.
Afterwards all those things that had an unshakeable grip on me started to become understandable in a way you'd understand ANOTHER person going through this, reasoning wasn't clouded anymore from my affection. I think that was the tipping point