Trending @Wipro; Had Reverse KT today. And I was completely blank.

I have cleared rev kt with my manager and TL. Both were on diff days. I cleared perfectly. Today I had rev kt with client, I was completely blank. He was asking the same questions which my manager asked I answered all to my manager and today was not able to ans a single question. Could not ans simple question. Now I'm so stressed out. What should I do?