falling in love with the help of nerve growth factor

this was all over the news in the past day. this write-up is from one of the prep services we use at the radio station.

'LOVE MOLECULE' ONLY LASTS A YEAR
Italian researchers have identified a molecule that triggers the powerful emotions felt by people who've fallen in love -- things like butterflies in the stomach, euphoria and a rapid heartbeat -- but it doesn't last any longer than a year. Researchers at Pavia University found far higher levels of the molecule known as nerve growth factor (NGF) in the blood of 58 people who'd recently fallen in love than in that of a group of singles and people in long-term relationships. However, after a year with the same person, quantities of the NGF "love molecule" had fallen to the same level as that of the other groups. The researchers said that it's not clear how falling in love triggers higher levels of NGF.

so, what do we do with the rest of it? how do we keep it going once the euphoric reaction has waned?