During the 100 days before the relationship starts, we observe a slow but steady increase in the number of timeline posts shared between the future couple. When the relationship starts ("day 0"), posts begin to decrease. We observe a peak of 1.67 posts per day 12 days before the relationship begins, and a lowest point of 1.53 posts per day 85 days into the relationship. Presumably, couples decide to spend more time together, courtship is off, and online interactions give way to more interactions in the physical world.
The process of falling in love has been variously described as giddiness, contentment and, in short, positive mood effects. That's because of the release of the biochemical effect of the release of dopamine in the brain, whose effects are similar to an amphetamine high. Diuk found a similar effect of heightened level of "happy" Facebook posts:
If you fall in love, your experience isn't that unique. Even Facebook knows the signs.