Who defiantly declared:

"Gentlemen, I wish you all to bear witness that, after a terrific strugle, I have conquered this goddamn willpower of mine."

after he tied one on at The Players, ending a protracted dry spell?

Rough guess...W.C Fields?

Close, but no seegar!

The man in question was an American newspaperman, poet, playwright, and ardent opponent of prohibition in the early 20th century. Here is a short sample of his poetry:

"There was a young fellow named Sidney
Who drank till he ruined his kidney
It shriveled and shrank
As he sat there and drank
But he had a good time of it, didn'e?"

Take another sip and it might come to you!!

That's gotta be Don Marquis!!

Very Nice!

One last quip from Mr. Marquis:

"Drinking used to be a mighty commonplace matter; but Prohibition has brought a smack of adventure into it that makes it really enjoyable."