Great that you list the brainwave functions here. Entering the theta and delta state fully consciously is possible, yet when we have never done before it can be highly energy draining within a matter of seconds. I remember the first time I entered that state fully awake in 2015 upon waking up in the morning, a few seconds alone were enough to exhaust my energy for the day almost completely. However, the more able we are to maintain higher energetic frequencies from day to day the less exhausting they become because we are becoming energetically more used to it. Thus far, it happened four times that I entered these states fully consciously ( it happens without control when it happens, I "slip" into them), and each time there was indeed very insightful information about my next life, which in turn greatly helped me understand the context of experiences, fear, dreams in this life, more specifically that everything is truly following a greater order. ;)