Life is not living, but living in health.

[Vita non est vivere, sed valere vita est.]

Martial (AD c.39-c.103) Spanish Roman poet, satirist, epigrammatist [Marcus Valerius Martialis]

Epigrams [Epigrammata], Book 6, epigram 70 (6.70.15) (AD 91) [tr. Ker (1919)]
    (Source)

(Source (Latin)). Alternate translations:

It is not life to live, but to be well.
[tr. Burton (1621)]

Not all who live long, but happily, are old.
[tr. Killigrew (1695)]

For sense and reason tell,
That life is only life, when we are well.
[tr. Hay (1755)]

For life is not to live, but to be well.
[tr. Johnson, in The Rambler, #48, cited to Elphinston (1 Sep 1750)]

To brethe can just not dying give:
But, to be well, must be to live.
[tr. Elphinston (1782), 2.115]

For life is not simply living, but living in health.
[tr. Amos (1858)]

Life consists not in living, but in enjoying health.
[tr. Bohn's Classical (1859)]

It is not life to live, but to be well.
[ed. Harbottle (1897)]

The blunderer who deems them so,
Misreckons life and much mistakes it,
He thinks 'tis drawing breath -- we know
'Tis health alone that mars or makes it.
[tr. Pott & Wright (1921)]

Life is not life, but health is life indeed.
[tr. Francis & Tatum (1924), #310]

To live is not just life, but health.
[tr. Shepherd (1987)]

Life is not being alive, but being well.
[tr. Shackleton Bailey (1993)]