"Hey, Elijah, you going out with Teresa tonight like you planned all month?"
"No man, her Selective Forgetness happened to kick in and she didn't ask her mom"
"Sorry man, I know you were really looking forward to it"
"Ya, but I don't want to be pulling a Teresa
Just like a music instrument without frets someone would be call fretless by having no constrait, limitation, or restriction. Saying someone is fretless is a sexy and colourful way of saying he or she seems free in a cool way.