Everything. Continuity is the biggest problem.
I study books in the Winter and have "My Kids" in the Summer. I was very lazy last Winter and had disinterested Kids this Summer.
I took a backwards step.
I can communicate at work: "полотенца до комнатной два три четыре пожалуйста." I know about the blonde bitch with the tattoo.
I can order a meal. I can order a beer (VERY IMPORTANT!). I can ask for directions, etc and understand the replies.
I am a good employer and visitor. I would like to know more. I doubt I will ever be "fluent" or translate Great Works.
I have dreams where I speak Russian fairly well. I use a slovar though.
I teach "My Kids" baseball at work. A lot of slang. A commentator is taking time off for personal reasons. He was replaced by Dennis Eckersley, a former pitcher. He uses a lot of slang. "Он бросает сыр". That won't confuse anyone!
Excuse me, Pardonais mois, I have to destroy French with a Quebecois Tour Bus.
Enjoy your stay!
Он бросает сыр