Late Night Brain Syndrome

The condition of your brain in which late at night you think of things that make you sad, such as memories with an Ex or just fun times that you wish you could repeat and relive forever.
It also includes thinking of someone you like, but knowing that they don't like you back, or you're too afraid to find out if they do or not, therefore, you will never get to be with them.

Jay: I am sad.
Ashlynn: Why's that?
Jay: My Late Night Brain Syndrome is kicking in. All I want to do is sleep but I can't stop thinking.