Q: 50s SF story about a man who is burdened with being the "life" of any party or assembly In the short story, he is a "life of the party" guy whom everyone admires and wants to be around, but when he gets home from the party, he sheds the burden of false animation and jollity as if it were a mask or suit of clothes, or even (in modern concept) an artificial "personality prosthesis".
If not 1950s might have been late 40s or early 60s. Male author, may have been fairly well known in that era (like Leinster, Matheson, etc but not like Asimov or Clarke).

A: This is probably "The Handler" by Damon Knight although it is a bit different from the description in the question.
The protagonist actually "drives" an artificial man "the big guy" who is literally the life of the party.  He is small and fits inside "the big guy".
In the story, the "big guy" comes to a party and is the center of attention, everyone loves him and wants to be with him, etc. etc. Suddenly the "big guy" announces "I want you to meet my handler." The little guy climbs out of "the big guy", and everyone ignores the little guy, brushes him off, wanders off to keep from talking to him, etc.
At the end, he climbs back into "the big guy" and it's party on again!

...the room was really jumping, it was a great party, and everything was all right far into the night.

The story is kind of surreal. It's no secret that "the big guy" is operated by the little guy. Everyone at the party knows both of them.
