To keep to oneself, to be secretive, to be very cautious in one's dealing with people and giving nothing much or nothing at all away. (As if one were playing cards and not permitting anyone to see any of the cards.)
"He is very cautious. He plays his cards close to his chest."
"You seem to be playing your cards close to your vest."
Pajama casual is a term used when working from home and preparing for a video conference. All business above the waist and your pajama pants down below.
We have a Zoom meeting in a few minutes and I’ll probably go pajama casual.