It is a big step to know this. Awareness is the first step to change. My guess is that when he is isolating, he can't remember this or can't believe it if he does even think of it. I have been there many times.

It would be helpful if he could accept this without judgement. It sounds like he beats himself up even with this awareness. Instead, he can soften it by saying, Oh yeah, I forgot how this works with me.

Ask him, when he is feeling good, if you could gently and non-judgementally remind him and reassure him of this. It might help. It might not help the first time, but it might eventually. It will also reinforce for him that you are there for him even when he is not there for himself.