Paraphrase: You turn into a cold, calculating (/machinating, /designing, etc.) creature who becomes [in turn] a person who is in a newfound state of mediocrity which they are not used to, and this difference allows you to see the difference between the self you desired [your dream or ideal self, as perceived by you] and the self you know currently [from which there is a large difference between it and your dream self, the fact which makes you disappointed].
People use different words to convey different tones. So whereas the writer may be human, he is referring to himself as a creature to make himself seem more dastardly and unlikeable, from whatever angle. Certain words convey a variety of meanings, and thus a variety of tones. You have to know what words these are in order to know what tone he's conveying.
I would say he's conveying a disillusioned tone if anything else. Please see the EnglishStackExchange for more on tone.