From Wikipedia

is characterized by intrusive thinking and pronounced sensitivity to external events that reflect the disposition of the limerent object towards the individual. It can be experienced as intense joy or as extreme despair, depending on whether the feelings are reciprocated. Unlike English, many other languages have traditional terms to denote limerence, like the German Verliebtheit or Russian влюблённость (vlyublyonnost); both expressions may roughly be translated to “fallen-in-love-ness”.

Limerence has certain basic components:
* Intrusive thinking about the limerent object.
* Acute longing for reciprocation.
* Some fleeting and transient relief from unrequited limerence through vivid imagining of action by the limerent object that means reciprocation.
* Fear of rejection and unsettling shyness in the limerent object's presence.
* Intensification through adversity.
* Acute sensitivity to any act, thought, or condition that can be interpreted favorably, and an extraordinary ability to devise, fabricate, or invent "reasonable" explanations for why neutral actions are a sign of hidden passion in the limerent object.
* A general intensity of feeling that leaves other concerns in the background.
* A remarkable ability to emphasize what is truly admirable in the limerent object and to avoid dwelling on the negative or render it into another positive attribute.