Limerence - Let's learn about Love the technical way...

Limerence

• a scientific study into the nature of romantic love.
  
• it is an involuntarycognitive and emotional state in which a person feels an intense romantic desire for another person, the limerent object.
• aka "having a crush" on, but unlike a crush, can last months, years or even a lifetime.
  
• 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.
  
• Traditional terms in German or Russian both may be translated to “fallen-in-love-ness”.

ok, search it on Wikipedia for more detailed explanation. I'll just quote some excerpts:

It is not entirely pleasant, and when rejection seems likely the thoughts focus on despair, sometimes to the point of suicide. The pleasantness or unpleasantness of the state seems almost unrelated to the intensity of the reaction. Although the direction of feeling, i.e. happy versus unhappy, shifts rapidly, the intensity of intrusive thinking alters less rapidly, and alters only in response to an accumulation of experiences with the particular limerent object.

Along with the emphasis on positive qualities perceived in the limerent object, and preoccupation with the hope for return of feelings, there is a fear that limerence will be met by the very opposite of reciprocation: rejection. Considerable self-doubt and uncertainty is experienced and it causes pain, but also enhances desire to a certain extent. However in most cases, this is what helps to eventually destroy the limerence if a suitably long period of time has passed without reciprocation - this can stretch up to about six years.

Although it appears that limerence blossoms under some forms of adversity, extreme caution and shyness may prevent a relationship from occurring, even when both parties are interested. This results from a fear of exposing one's undesirable characteristics to the limerent object.

Limerence develops and is sustained when there is a certain balance of hope and uncertainty.The base for limerent hope is not in objective reality but reality as it is perceived. "Little things" are noticed and endlessly analyzed for meaning.

The physiological correlations of limerence are heart palpitations, trembling, pallor, flushing, pupil dilation and general weakness. Awkwardness, stammering, shyness, and confusion predominate at the behavioral level. There is apprehension, nervousness, and anxiety due to terrible worry that any action may bring about disaster. Many of the commonly associated physiological reactions are the result of the limerent fear.