I think I have to agree with you here as well, as desire runs more closely to instinct than reason does.
I think reason is what keeps us from being a slave to our desires and impulses. It's the higher voice within us that can look at what our monkey brain has to suggest and say "hey, that might not be such a good idea."
In regards to if it is "you"or not, within the context of what we are comparing I would say desire is much closer, but our desires are not "us" fundamentally.
But, of course, if we knew what "I" and "you" really mean, philosophy wouldn't even exist!