Oneitis

If a person focuses on an attractive person for too long, they begin to fantasize about, being with them forever.. They start naming babies, going through fake interactions in their mind, and building that person up in their imagination.
Strong feelings of a crush soon follow, and the person gains the distinct impression of "this one is different" this one isn't like the rest.

Ofcourse, the person is just like the rest of us, its just the dreaded disease of Oneitis striking.
Oneitis, makes you get out of touch with reality.. Its not to be confused with love. It is completely UNFOUNDED.
It creates intense and powerful feelings, that do not help in seducing your partner.. it will make you needy, and clingy.. And you'll creep them out by saying "I love you" too early.

So the solution is "quit thinking about them".. Don't think about attractive people for too long.. Keep preoccupied with other things, and hobbies.
Don't focus on it too much.