I know I'm forgetting something
When your brain is like, 'Something’s missing, but I don’t know what, and I don’t want to admit it.' You feel like a dumbass for not remembering it yet.
He was on the bus to work and thought, 'You forgot your coffee!' He had to run back and grab it, and it was cold by the time he got there.
She was at the grocery store and thought, 'You forgot your wallet!' She had to go home and get it, and then the store was out of her favorite cereal.
He was about to go on a date and thought, 'You forgot your shoes!' He ran back home, put on shoes, and then realized he forgot his socks.