​My kids are sentimental.  To the point of high drama and tears. I don't know where they get it from (says the woman who may or may not have  kept every tooth my children lost until my husband called me out on it.) So when they bring home their projects and art and every slip of paper they have ever scratched a doodle on, they want to keep it. "It's special to ME!!"  So, I learned to put them on top of the refrigerator and leave them there for a few days. If they ask for them again within those few days, I can say, "Here it is sweetie-I'd never throw that away. I know it's special to you."  (Hero points) and if not, when they are asleep or at school, I can throw them away.  Occasionally backfires but then I put it back on them, "If it was special, you should have put it in your room."