Maybe you enjoyed the game but once you realised that you were nearing it's end, wanted to be over and done with it. Unfortunately, I can get like this with a lot of games no matter how much I liked them. I'm constantly looking forward to the "next thing."
The perfect example I could give for me recently would be Dragon Quest XI S. Don't get me wrong, I enjoyed the game. But, it took me roughly 56 hours to beat. Which is considered to be the average amount in order to beat the main story.
(For some strange reason, I never grew tired of Dragon Quest VII on the 3DS though. That's considered an even longer game too. Even though I beat it in the same amount of time from memory.