All wines don’t turn sour when they get old, and neither do all men or all personalities. I approve of sternness in the old, but a sternness that, like other things, is kept within limits; under no circumstances do I approve of bad temper.
 
[Ut enim non omne vinum, sic non omnis natura vetustate coacescit. Severitatem in senectute probo, sed eam, sicut alia, modicam; acerbitatem nullo modo.]

Marcus Tullius Cicero (106-43 BC) Roman orator, statesman, philosopher

De Senectute [Cato Maior; On Old Age], ch. 18 / sec. 65 (18.65) (44 BC) [tr. Copley (1967)]
    (Source)

(Source (Latin)). Alternate translations:

For as every wyne long kept and olde waxith not eagre of his owne propre nature, right so all mankynde is not aygre fell cruell ungracious chargyng nor inportune in olde age of their owne kynde though some men among many be fonde of that condicion. I approve & preyse in olde age the man which hath severitee & stidfast abydyng in hym. Seuerite is contynuance & perseverance of oon maner of lyvyng as wele in the thyngys within as in theym withoute. But I approve nat that in an olde man be egrenesse nor hardnesse & sharpnesse of maners of condicions.
[tr. Worcester/Worcester/Scrope (1481)]

For even as every wine being old and standing long is not converted into vineigre, so likewise is not every age sour, eigre, and unpleasant. Severity and sternness in old age I well allow and commend, so that a moderate mean therein (as in all other things) be observed; but bitterness and rigorous dealing I can in no wise brook nor away withal.
[tr. Newton (1569)]

For as all wines do not grow soure and tart in continuance, so not all age. I like severity in an old man, but not bitternesse.
[tr. Austin (1648), ch. 19]

Our nature here, is not unlike our wine,
Some sorts, when old, continue brisk, and fine.
So Age's gravity may seem severe,
But nothing harsh, or bitter ought to appear.
[tr. Denham (1669)]

In short, as it fares with Wines, so it does with Old Men: all are not equally apt to grow sour with Age. A serious and moderately grave Deportment well become us, but nothing of an austere Severity.
[tr. Hemming (1716)]

Thus it is, for as all Wines are not prick'd by Age, so neither is Human Life sower'd by Old Age; a Severity I approve of in Old Men, but with Moderation; Bitterness by no means.
[tr. J. D. (1744)]

Some Wines sour with Age, while others grow better and richer. A Gravity with some Severity is to be allowed; but by no means Ill nature.
[tr. Logan (1744)]

As it is not every kind of wine, so neither is it every sort of temper, that turns sour by age. But I must observe at the same time there is a certain gravity of deportment extremely becoming in advanced years, and which, as in other virtues, when it preserves its proper bounds, and does not degenerate into an acerbity of manners, I very much approve.
[tr. Melmoth (1773)]

For, as not every wine, so not every life, grows sour by age. Strictness in old age, I approve; but that, even as other things, in moderate degree: bitterness I nowise approve.
[Cornish Bros. ed. (1847)]

Neither every wine nor every life turns to vinegar with age.
[ed. Harbottle (1906)]

For as it is not every wine, so it is not every man's life, that grows sour from old age. I approve of gravity in old age, but this in a moderate degree, like everything else; harshness by no means.
[tr. Edmonds (1874)]

For as it is not wine of every vintage, so it is not every temper that grows sour with age. I approve of gravity in old age, so it be not excessive; for moderation in all things is becoming: but for bitterness I have no tolerance.
[tr. Peabody (1884)]

The fact is that, just as it is not every wine, so it is not every life, that turns sour from keeping. Serious gravity I approve of in old age, but, as in other things, it must be within due limits: bitterness I can in no case approve.
[tr. Shuckburgh (1895)]

Not every wine grows sour by growing old.
Severity in age is well enough:
But not too much, and naught of bitterness.
[tr. Allison (1916)]

As it is not every wine, so it is not every disposition, that grows sour with age. I approve of some austerity in the old, but I want it, as I do everything else, in moderation. Sourness of temper I like not at all.
[tr. Falconer (1923)]

Human nature is like wine: it does not invariably sour just because it is old. Some old men seem very stern, and rightly so -- although there must be, as I always say, moderation in all things. There is never any reason for ill temper.
[tr. Cobbold (2012)]

Certainly neither all wines go sour
Nor do all men because of agedness.
I approve of old men’s calm severity,
But I don’t put up with those who are dour.
[tr. Bozzi (2015)]

The truth is that a person's character, like wine, does not necessarily grow sour with age. Austerity in old age is proper enough, but like everything else it should be in moderation. Sourness of disposition is never a virtue.
[tr. Freeman (2016)]