They say love is the drug
...depends on what type of drug
Love is like Zoloft. It causes a permanent improvement over time, but it does not shield you from the ups and downs of everyday living. You will still feel pain, you will still fight, you will still be upset now and then. Love, like Zoloft (if it works with your body chemistry like it's supposed to) does not change who you are but it makes the day to day a lot more pleasant.
Infatuation, or lust, on the other hand is like alcohol. The buzz is short-lived but very apparent. The first time you say "I'm interested in you" and get that favorable response from the other will eradicate any worry you have had at the time. The nervous glances, subtle innuendo and careful treading on ground you have never seen before causes a high that makes your head spin and causes shallow breathing and tachycardia, although it is not unpleasant at all.
Infatuation can be very addictive. You will spend the rest of the relationship trying to recreate the initial high but you never will be able to. Tolerance can be overcome by a change of scenery, or a different focus of attraction, and the cycle starts over again.