A vow taken in order to pledge to refrain from constantly messaging, liking and/or commenting on statuses of your crush.
In other words, you force yourself to completely ignore your crush online so that you can make an attempt to converse with them in person.
This vow prevents the insomnia and/or obsession caused by non-stop Facebook checks in order to see if the said crush has replied or paid any attention to the crush-ee.
"Man, Laura is totally Facebook stalking David!"
"Yeah, she needs to take a Facebook chastity vow."
"Susan still hasn't replied to my comment! I can't stand this!"
"Dude- chill. Take a Facebook chastity vow and cool your jets"