I stopped playing BO2 for probably two months. I came back nearly two weeks ago and have been enjoying significant improvement.
I played all the other CODs since and including MW1 during my break from BO2. For those games, I just played like I'd always played. Without thinking about it, that's how I came back to BO2. For some reason, when these games come out, I tend to hit the floor running and doing very well ... then quickly nose dive down to a little over a 1.5 kdr and 45% wlr. With time, though, I begin improving quite a bit.
So, for me, it was not that I did not adapt to BO2. I did change the way I played and that ended up hurting me. When I took a IDGAF attitude and just played the way I had always played, things have gotten much better.