I still should not want you to smile on all occasions:
for nothing is more silly than a silly smile.

[Tamen renidere usque quaque te nollem;
Nam risu inepto res ineptior nulla est.]

Catullus (c. 84 BC – c. 54 BC) Latin poet [Gaius Valerius Catullus]

Carmina # 39 “To Egnatius,” ll. 15-16 [tr. McDonnell (1998)]
    (Source)

(Source (Latin)). Alternate translations:

E'en then that ceaseless ill-tim'd grin forego:
A silly laugh's the silliest thing I know.
[tr. Nott (1795), # 37]

I'd say renounce thy ceaseless idiot grin,
A silly laugh is folly, if not sin.
[tr. Cranstoun (1867)]

Yet sweetly smiling ever I would have you not,
For silly laughter, it's a silly thing indeed.
[tr. Ellis (1871)]

Yet thy incessant grin I would not see,
For naught than laughter silly sillier be.
[tr. Burton (1893)]

Still I wish you wouldn't grin forever everywhere; for nothing is more senseless than senseless giggling.
[tr. Smithers (1894)]

Still I should not like you to be smiling everlastingly; for there is nothing more silly than a silly laugh.
[tr. Warre Cornish (1904)]

I would have you drop your endless grin: for nothing is more inane than inane laughter.
[tr. Stuttaford (1912)]

Still not to smile for aye is wisdom's rule:
For folly's laugh proclaims the peerless fool.
[tr. MacNaghten (1925)]

I still should still disapprove that constant smile;
It shows a silly, poor, affected style.
[tr. Wright (1926)]

Your smile would still offend me; nothing is worse
than senseless laughter from a foolish face.
[tr. Gregory (1931)]

I still wouldn't want to see you always grinning,
for nothing is more inept than inept laughter.
[tr. C. Martin (1979)]

I’d still not want you to smile all the time:
there’s nothing more foolish than foolishly smiling.
[tr. Kline (2001)]

I'd still not want you flashing yours all round since
nothing's more fatuous than a fatuous grin.
[tr. Green (2005)]

I still should not want you to smile on all occasions:
for nothing is more silly than a silly smile.
[tr. Wikisource (2018)]