The act of showing too much interest in another person making you appear desperate and less desirable to them. The term "Quick Sanding" is referring to if you were standing in quick-sand trying to get out- the harder you try the quicker you will sink.
Her: "I tried calling him, texting him, even went to dinner with his mom. Then I tried to add him on Facebook. I still haven't got any response. I know....I will try texting him again!"
Person listening to her: "You are Quick Sanding so bad right now- Please just stop!"
Awesome movie with awesome music set in the early 1960's in the San Fernando Valley :)
from IMDB:
Scotty Smalls moves to a new neighborhood with his mom and stepdad, and wants to learn to play baseball. The neighborhood baseball guru Rodriquez takes Smalls under his wing, and soon he's part of the local baseball buddies. They fall into adventures involving baseball, treehouse sleep-ins, the desirous lifeguard at the local pool, the snooty rival ball team, and the travelling fair. Beyond the fence at the back of the sandlot menaces a legendary ball-eating dog called The Beast, and the kids inevitably must deal with him.