I think the rational (mostly linguistic) parts of our brain can influence decisions made by other parts, if we're smart about it. The main trap seems to be that when the conscious and subconscious parts of our brain disagree, we may decide that we didn't will hard enough. So we try to "will harder", which to the linguistic part of our brain means sticking the word "very" in front of everything and generating a bunch of negative self views, which has the opposite of the desired effect on our subconscious.
IAWY; it's either the opposite effect, or just no effect. You could also think of this as being a case of "the leader not listening to subordinates", in that the "try harder" mode is ignoring whatever the actual problem is -- i.e., the subconscious goal or prediction that's interfering. In my experience it's much more important to teach people to be able to listen to themselves (i.e., become aware of what they already believe/expect/desire) than to talk to themselves (i.e., push new information in).
Every time I try listening to myself, my subconscious invents me some new and "deep" explanation that I then actually believe for a day or two. It's an endless quest.
A more fruitful strategy for me was taking some minutes or hours every day to grow something new in my mind, ignoring the old stuff completely. A couple times the new stuff in me eventually grew strong enough to overthrow the old stuff for control of my life without much struggle.
Much has been written here about the issue of akrasia. People often report that they really, sincerely want to do something, that they recognize that certain courses of action are desirable/undesirable and that they should choose them -- but when the time comes to decide, they do otherwise. Their choices don't match what they said their choices would be.
While I'm sure many people are less than honest in reporting their intentions to others, and possibly even more who aren't even being honest with themselves, there are still plenty of people that are presumably sincere and honest. So how can they make their actions match their understanding of what they want? How can their choices reflect their own best judgment?
Isn't that really the wrong question?
If a model of a phenomenon fails to accurately predict it, we conclude that the model is flawed and try to change it. If what we're trying to understand is ourselves, our own choices, and the motivations, desires, and preferences that direct those choices, why should we do any differently? Our actions reveal what we actually want, not what we believe we want or believe we should want. No one chooses against their own judgment. What we do is choose against our understanding of our own judgment, and that is a far subtler matter. By our fruits shall we know ourselves.
Expecting our behavior to be constrained and controlled by our understanding is like expecting our limbs to move if we yell at them to do so. It doesn't matter how much we believe we want them to move, or how much we say we want them to move. It is irrelevant whether we have a conscious understanding of the nerves and muscles involved. Our conscious awareness is a bystander that reports what happens and attributes its observations to itself, when in actuality it controls very little at all.
There are people whose ability to move has been damaged by nerve trauma or damage to the brain. The established relationships between their intents, their desires, and the signals to their muscles, have been damaged or destroyed. Such people do not improve by talking to others about how much they want to move, or by talking to themselves about it (which is what conscious thought really is). They get better by searching out connections that work and building on them.
Babies have little if any consciousness, and they don't possess theory. Their nervous systems learn to move their bodies by bombarding their muscles with random noise triggered by their interests, and strengthening the signals that happen to get them closer to what they want. Not what they think they want. It is quite unlikely that babies have models of their minds, much less conscious ones, although they are either born with models of their bodies or the foundations for building such a model.
Those who wish to bring themselves into alignment with what is truly correct, instead of what their impulses and desires seek in themselves, must first understand the nature of their impulses and the nature of their understanding.