The euphoria of falling in love (as in the love-at-first-sight kind of love as opposed to the let's-get-married type) isn't logical. We might rationalize it afterwards (i.e. it was her eyes...) but more often than not, the experience is an ambush, something you didn't expect and you're abandoned to deal with the consequences.
It's amazing how our body reacts to such a state. You're confused and you act in the most unexpected of ways. Even more interesting is the enzymes and chemicals that our bodies secrete. Whether it's the ecstasy or the depression kicking in, you transcend your normal limits. You might subsist on little food and little sleep. You shrug off concerns that would otherwise alarm you. You manage to accomplish physical feats such as jogging that extra mile or lifting a few additional pounds.
For good or for ill, this heightened state doesn't last long. It goes as easily as it came. I mean no matter how much you will it, it won't suddenly manifest itself (or go away). For me, it's like attempting to trap lightning in a bottle. Some things, however, cannot be tamed.