The very first part of the quote, "When you actually do not like a guy, they're all over you", suggests that there is frequently a boost in attention and pursuit from somebody you aren't particularly thinking about. This might be explained by the notion that an absence of interest or accessibility can make one seem more intriguing or elusive. When an individual is not overtly chasing after someone's attention, it may unintentionally raise their social value in the eyes of others, triggering increased interest. In psychological terms, this can be described as 'reactance' where people prefer what they view as being out of reach or limited.
Conversely, the second part of the quote, "as quickly as you imitate you like them, they're no longer interested", shows the phenomenon where revealing reciprocal interest can dampen the other person's interest. This might be connected to the human propensity to worth what they need to work harder to obtain. When the difficulty is gotten rid of, the pursuer may lose interest since the excitement of the chase is diminished. It highlights the delicate balance in relationships where too much openness in one's sensations can possibly minimize the perceived obstacle and reduce intrigue.
