"He Still Remembered That He Once Was Young"

Context: John Armstrong, a physician, wrote The Art of Preserving Health in four books: Air, Diet, Exercise, and The Passions. Book IV, on The Passions, is a treatment of those internal factors that influence health, the first three books being on externals. After, however, stating that the passions should be kept in moderation, the author treats the subject of love. An unfortunate result of disappointed love is often the resort to inordinate wine-drinking. Armstrong by no means advocates total abstinence from wine, as he has high regard for the virtues of port, champagne, Burgundy, and Rhine wine; but he does deplore drunkenness. While intoxicated, a person can say a word that will lose a friend; he can perform a deed that will haunt him to the grave. Drink will cause the means, the health, the talents to decay and will produce a brutishness that will cause a man to be unrecognizable to those who know him. The author then says that he will give precepts for a happy life, enunciated by a certain virtuous old man:

How to live happiest; how avoid the pains,
The disappointments, and disgusts of those
Who would in pleasure all their hours employ;
The precepts here of a divine old man
I could recite. Though old, he still retained
His manly sense, and energy of mind.
Virtuous and wise he was, but not severe;
He still remembered that he once was young;
His easy presence checked no decent joy.
Him even the dissolute admired; for he
A graceful looseness when he pleased put on,
And laughing could instruct. Much had he read,
Much more had seen; he studied from the life,
And in th' original perused mankind.
. . .