What one has, one ought to use; and whatever he does he should do with all his might.

[Quod est, eo decet uti: et quicquid agas, agere pro viribus.]

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

De Senectute [Cato Maior; On Old Age], ch. 9 / sec. 27 (9.27) (44 BC) [ed. Hoyt (1882)]
    (Source)

On failing strength in old age.

(Source (Latin)). Alternate translations:

A man ought wele for to use in every age of that thyng that nature giveth hym, and also it apperteyneth that thou doo alle thyngs aftir the mesure and aftir the quantyte of thyne owne propre strength and not to usurpe and take the unto gretter thyngs than thou maist not nor hast no power to execute.
[tr. Worcester/Worcester/Scrope (1481)]

For whatsoever is engraffed naturally in man, that is it fit and decent to use; and in all things that he taketh in hand to labour, and to do his diligent endeavour according to his strength.
[tr. Newton (1569)]

For that which is naturally ingraffed in a man, that it becommeth him to use, and to desire to do nothing above his strength.
[tr. Austin (1648)]

Then with that force content, which Nature gave,
Nor am I now displeas'd with what I have.
[tr. Denham (1669)]

What strength and vigour, we have still remaining, ought to be preserv'd, by making the best use of them while we are able.
[tr. Hemming (1716)]

What a Man has, he ought to use; and whatever he does, to do it according to his Power.
[tr. J. D. (1744)]

For it is our business only to make the best use we can of the powers granted us by nature, and whatever we take in hand, to do it with all our might.
[tr. Logan (1750)]

It is sufficient if we exert with spirit, upon every proper occasion, that degree of strength which still remains with us.
[tr. Melmoth (1773)]

What is, that it becomes you to employ; and whatever you do, to do it according to the measure of your powers.
[Cornish Bros. ed. (1847)]

What one has, that one ought to use; and whatever you do, you should do it with all your strength.
[tr. Edmonds (1874)]

It is becoming to make use of what one has, and whatever you do, to do in proportion to your strength.
[tr. Peabody (1884)]

You should use what you have, and whatever you may chance to be doing, do it with all your might.
[tr. Shuckburgh (1900)]

What nature gives to man, that let him use:
Still fit your work according to your strength.
[tr. Allison (1916)]

Such strength as a man has he should use, and whatever he does should be done in proportion to his strength.
[tr. Falconer (1923)]

Use what you have: that is the right way; do what’s to be done in proportion as you have the strength for it.
[tr. Copley (1967)]

Whatever strength you have at any given moment, you should use; and whatever you do, you should do it within the limitations of that strength.
[tr. Cobbold (2012)]

You use what you have and gauge your activities accordingly.
[tr. Gerberding (2014)]

You see, It’s a lot better to proceed
With your own strength and anything you do
According to your strength you should pursue.
[tr. Bozzi (2015)]