The warm, happy, euphoric narc is pretty rare in cold, dark water. What is far more common, at least here in the PNW, is free-floating anxiety and tunnel vision -- lack of situational awareness. One of the things my husband does with the deep dive for his AOW class is to tell the students they are to log their depth and pressure at five minute intervals through the dive. Funny, at about 80 feet or so, most of them start forgetting to do it . . . That's narcosis, and can end up with severe anxiety when somebody realizes they are much deeper than they want to be with the amount of gas they have left, just as you did.
It was good that you did not panic. It was good that the ascent was controlled, and that you made a conscious decision not to do the safety stop, although it appears you probably could have, if you could have calmed yourself at that point.
You nailed most of the lessons here. A dive plan should include a gas plan, and although I do not plan all dives on rule of thirds, as Joel mentioned, I do always calculate a "rock bottom", or the amount of gas that needs to be reserved to get me and my buddy from the deepest point of the dive to the surface, sharing gas. Had you been a little more distracted, you might well have ended up in that situation -- did your buddy have enough gas to get you home? These are important things to consider, particularly on very deep dives like this one.
