Apart from the rather extreme example JD mentions, I'm not sure that there ever could be a true "I" all the way down, if only because the brain supports massive parallelism. To use the simple examples Moonbat mentions, it would take a we to cope consciously with digestion, breathing, dribbling the ball all at the same time. And yet that's just a small fraction of what anyone dribbling a ball is doing, all at the same time.
Regarding the assertion that
none of our decisions are made by our conscious selves, I'm not sure that's true. Suppose you were buying a house and had written down a list of suitable criteria (number of bedrooms; near to/far from a busy road; near a good school; off street parking/garage; sea view; close to/far from a station; that sort of thing). While your subconscious might affect what was on the list - although these things don't tend to be spur of the moment choices, particularly where a couple, or a whole family, is involved in drawing the list up - I think the conscious mind would be completely on board with the result. Then comes the disappointment that goes with meeting those criteria using the budget you have. But let's assume there's a house that meets them all, and another house that "feels right".
If you were to choose the latter, rather than pick the most suitable house,
I wouldn't call that rational thinking (whether the I was the conscious I or some subconscious process), but "going with a hunch" or, to be rather less kind, wishful thinking. You might, later, say that you were happier in that house than you would have been in the suitable one, but as with all such decisions in real time, that's no more than an opinion (as there's no way to make a true comparison**). If you chose the suitable house, it seems to me that that is both rational and the result of a rational, conscious process.
Some of us are anal enough (not that I'm saying that the relevant decisions are made
that far away from my conscious self
) to make lists when we buy things: cars, cash ISAs***, houses, audio equipment, PCs, peripherals....
However, I do concede that even I am probably driven by my subconscious's decision making for much of what I (decide to) do. I simply do not believe (and my subconscious - which as Moonbat points out, is still me, agrees with me, though probably complexly) that's the case all of the time.
** - Unless the "suitable" house was, say, hit by a juggernaut or a meteor.
*** - Tax-free savings accounts.