Basically the guy is going through a break up and can't get over the guy. "I been tryna get you off my mind, but I can't after all this time" and "when i’m with somebody all i think 'bout is you (yeah)
when i’m all alone that’s all i wanna do (yeah)" They ahd a great relationship and he really liked her, so now all he can think about is her even though he's tryin to move on, and even though he is trying so hard he still really WANTS to think about her.
Basically the guy is going through a break up and can't get over the guy. "I been tryna get you off my mind, but I can't after all this time" and "when i’m with somebody all i think 'bout is you (yeah) when i’m all alone that’s all i wanna do (yeah)" They ahd a great relationship and he really liked her, so now all he can think about is her even though he's tryin to move on, and even though he is trying so hard he still really WANTS to think about her.