Term used to let go of ill will after being upset, preoccupied or concerned about something negative that is consuming someone's thoughts. This term is derived from clearing you cookies in your internet options in order to surf online smoothly.
Could be used to help a friend get over a moral hangover. For instance, your buddy is beating himself up about the drunk dial he made to an ex girlfriend or about the rude comment he made to his boss at the office party. You let him revel in his misery until about 4pm and then it's time to say "Dude, clear your cookies, move on. It's not a big deal...let's play nintendo and order a pizza."