You've got a friend who keeps a running tally of everything. If they did you a favour, you owe them. If they shared their snack once, they'll remind you of it weeks later when they want something. "I let you borrow my stuff, so you have to let me…" Every kind thing they've done comes with an invisible receipt, and sooner or later they cash it in. You're starting to feel like you can never just accept a nice gesture from them, because it's never really free — it's a deposit they'll withdraw later, usually to get you to do something you don't want to do.