NEW YORK -- I woke up one day last week and found myself 70 years old. It is a matter of scanty moment; my rounds will go pleasurably on as they always have, world without end, until my masters trade me in at the antiques show for some dubious bit of art deco. Still, the recollections press an unexpectedly insistent claim: I have stood twice in St. Peter's Square and heard the oldest cardinal raise the glad cry, ''Habemus Papam,'' once for Angelum Roncallus and once for Johannes Lucianus, and not Henry James, nor Stendhal nor, for that matter, Michelangelo could ever have said the same.

I have had breakfast with Frank Costello, who commended me for the alacrities of my appetite and said that he owed his long life to three axioms. The first was ''Always eat a large breakfast.'' The second was ''Never try to cheat on your taxes.'' He forbore to mention the third, an abjuration perhaps to avoid sitting with one's back to a window.

I have sat a little after twilight in the Dexter Memorial Baptist Church in Montgomery, Ala., with the congregation singing low and stirring to joy at the entrance of a young man who wore a hat so broad-brimmed that I took him for a sideman in the house band and who turned out, of course, to be Martin Luther King.

I have seen Robert Kennedy with his children and John Kennedy with the nuns whose fidelity to their eternal wedlock to Christ he strained as no other mortal man could. I have been lied to by Joe McCarthy and heard Roy Cohn lie to himself and watched a narcotics hit man weep when the jury pronounced Nicky Barnes guilty. Dwight D. Eisenhower once bawled me out by the numbers, and Richard Nixon once did the unmerited kindness of thanking me for being so old and valued an adviser.

But, if I have feasted with a panther or two, I can remember supping with only one god and that one had been left without an undeflected worshiper except myself. It was Westbrook Pegler, and he observed at lunch that he had been misunderstood by those who imagined that he had been driven crazy by Mrs. Roosevelt. That, he said, was not the case at all.

''It began,'' Peg explained, ''when I quit sports and went cosmic. It finished when I began writing on Monday to be printed on Friday.''

That gospel has been so rooted in my heart ever since that I write every day for the next and walk wide of the cosmic and settle most happily for the local, a precinct less modest than I make it sound, since my local happens to be the only city under the eye of God where the librettist for ''Don Giovanni'' could find his closest friend in the author of ''The Night Before Christmas.''

I talked with Louis Armstrong one night in Basin Street and mentioned his record of ''When You're Smilin','' which I had early loved and too soon lost. ''I was working in the house band at the Paramount when I was young,'' Armstrong said. ''And the lead trumpet stood up and played that song, and I just copied what he did note for note. I never found out his name but there was kicks in him. There's kicks everywhere.'' And then he went back to the stand and played ''When You're Smilin','' still thinking it remembered note-for-note even while he was quite transcending it, and he had made immortal a figure never vivid and faded long ago.

There are, in truth, kicks everywhere, and I have had all these and never one at my own expense. Most of life's epiphanies arise from its accidents, and it is never so much fun as when it conscripts us as prisoners to the luck of the day. Colette says in ''The Vagabond,'' that bible for all us migratory laborers, that ''If Chance ever got Herself called God, I should have been a very good Catholic indeed.'' And so, too, should I.