changing feelings

What do you think about the following quote. It is a bit of a challenge to my current thinking.
"A bad feeling is not dispelled by conscious effort or willpower. It can be dispelled, however, by another feeling. If we cannot drive out a negative feeling by making a frontal assault on it, we can accomplish the same result by substituting a positive feeling. Remember that FEELINGS FOLLOW IMAGERY. Feeling coincides with, and is appropriate to, what our nervous system accepts as real or the truth about environment. Whenever we find ourselves experiencing undesireable feelings, we should not concentrate on the undesireable feeling, event to the extent of driving it out. INSTEAD, we should immediately concentrate on positive imagery, on filling the mind with wholesome, positive, desireable images, imaginations, and memories. If we do this, the negative feelings take care of themselves. They simply evaporate. We develop new feeling-tones appropriate to the new imagery." (The New Psycho-Cybernetics, Maltz, p.275-276)