Day + Borrow. It means to borrow your emotions from another day either past or future to satisfy your emotional needs today. This could be done in a negative or positive light.
"Yesterday was so awesome. I was around all my friends having the time of my life. And now .... I'm at work, with co works who seriously don't give a shit about each other. If I'm gonna make it through this shift I'm gonna have to daeborrow from yesterday or else I'm not gonna make it."