To be honest, the last 2-3 games have been this way. Pikmin 3/Sleeping Dogs was the same way, I was on the last level of those games for a few days before actually finishing them. It's kinda weird, like I sort of just stop playing right at the end even if I'm really enjoying the game. I finished them and I'll finish this one too, but I'm like "eh, I'll do it later" even if I have nothing to do and enjoy the game.
Maybe I need to go see a gamer's psychologist and figure out the problem?
I have done that a lot before as well. Not sure why. I can even be bored and still not finish the game.