My friend H has been here most of a day, and I've been nattering on in Japanese without too much problem (to the amusement of Chinese bystanders). At two kinds of juncture, though, I sense that same paralysis approaching. The first is when a very ordinary word won't come to me - the Chinese word just squats there and won't let anything else through. That happened with the word twenty, whose Japanese I suddenly couldn't remember for the life of me or even reconstruct.
The second is more basic still - I can't get a sentence started because I'm thinking the Chinese sentence, whose structure is different; indeed I can't recall how to start the sentence in either language! That happened a few times as I tried chatting to myself in Japanese in preparation for H's visit; I find I need to leap into a sentence already in motion, since the starting point to speaking in Chinese won't disclose itself to me. It sounds odd, I'm sure, but I can get off and running if I can jump into a multisyllabic phrase like なかな出来ない or 思ったほど難しくない. Still I got stuck trying to say I had two slices of bread for H's breakfast and was reduced to English! 恥ずかしい and 不好意思了!
I suppose I ought tbe rejoicing that Chinese got into my system enough to cause such problems, huh!
(Picture above: the smog-reddened moon reminded H of the 日の丸.)