I know, you always come out on top, the great exception.
Well, someday your enemies will laugh and laugh. Consider:
life is full of changes, and who can stand them better? A man
who treats his body and proud mind to luxury, addicting them,
or someone used to little, and to thinking of the future,
a man wise in peacetime, preparing then the tools of war?

[Uni nimirum recte tibi semper erunt res,
o magnus posthac inimicis risus. Uterne
ad casus dubios fidet sibi certius? Hic qui
pluribus adsuerit mentem corpusque superbum,
an qui contentus parvo metuensque futuri
in pace, ut sapiens, aptarit idonea bello?]

Horace (65-8 BC) Roman poet, satirist, soldier, politician [Quintus Horatius Flaccus]
Satires [Saturae, Sermones], Book 2, # 2, “Quae virtus et quanta,” l. 106ff (2.2.106-111) (30 BC) [tr. Fuchs (1977)]
    (Source)

Reply when a rich person argues with the narrator that they are so wealthy they need not be concerned about wasteful spending. The last line, about a wise man preparing for war during times of peace, is often quoted on its own.

(Source (Latin)). Alternate translations:

O ieste, unto thy very foes, for, whether may have more,
(If fortune frowne, and grefes growe on) esperance to his store?
Thou: which was maried to thy mucke, and freshe in gay attyre,
Or he: that dreading chaunce to cum, a litle doth desyre,
And keepes it well, and warylye to helpe in hopelesse tyde:
Lyke as the wyse in golden peace for stormye warre provide.
[tr. Drant (1567)]

Cant thou suppose
Thy fate alone will still be prosperous;
Oh, how thine enemies will laugh at thee,
When thou'rt reduc'd to want and beggary!
Which of the two can certainest rely
On his own temper in adversity?
That man whose pamper'd body and his mind,
Have ever been to luxury inclin'd,
Or that's content with little, and doth fear
What may fall out, and wisely does prepare
In time of peace things requisite for war.
[tr. A. F.; ed. Brome (1666)]

Kind fortune still, forsooth, shall smile on Thee,
O future sport unto thine Enemy!
And which is better able to endure
Uncertain Chance? And which lives most secure?
He that doth never Fortune's smiles distrust,
But Pampers up himself, and feeds his Lust?
Or He that lives on little now, and spares;
And wisely when 'tis Peace, provides for Wars?
[tr. Creech (1684)]

Shalt thou alone no change of fortune know?
Thou future laughter to thy deadliest foe!
But who, with conscious spirit self-secure,
A change of fortune better shall endure?
He, who with such variety of food
Pampers his passions, and inflames his blood,
Or he, contented with his little store,
And wisely cautious of the future hour,
Who in the time of peace with prudent care
Shall for the extremities of war prepare?
[tr. Francis (1747)]

Shalt thou alone feel no reverse? Shalt thou
Thrive on for ever as thou thrivest now?
Poor child of scorn! Say which with better grace
May dare to look pert Fortune in the face --
The man that still in luxury's lap reclined
Pampers his body and unnerves his mind --
Or he that, with a little well content
And of his future comforts provident,
Like a wise chief is cautious to prepare
In time of peace the requisites for war?
[tr. Howes (1845)]

What, will matters always go well with you alone? 0 thou, that hereafter shalt be the great derision of thine enemies! which of the two shall depend upon himself in exigences with most certainty? He who has used his mind and high-swollen body to redundancies; or he who, contented with a little and provident for the future, like a wise man in time of peace, shall make the necessary preparations for war?
[tr. Smart/Buckley (1853)]

No doubt on you alone will fortune never cease to smile! O you doomed soon to be great source of laughter to your enemies when all your wealth is spent! Now which of these two characters will have a surer self-reliance 'gainst reverse? The one who has long used his haughty mind and pampered frame to luxury, or he who, satisfied with humble life, and careful of his future lot, like a good general has well prepared for war in time of peace.
[tr. Millington (1870)]

Ay, you're the man: the world will go your way ...
O how your foes will laugh at you one day!
Take measure of the future: which will feel
More confidence in self, come woe, come weal,
He that, like you, by long indulgence plants
In body and in mind a thousand wants,
Or he who, wise and frugal, lays in stores
In view of war ere war is at the doors?
[tr. Conington (1874)]

You alone, of course, will always find things go well. Oh, what a laughing-stock you will be some day for your enemies! Which of the two, in face of changes and chances, will have more self-confidence -- he who has accustomed a pampered mind and body to superfluities, or he who, content with little and fearful of the future, has in peace, like a wise man, provided for the needs of war?
[tr. Fairclough (Loeb) (1926)]

For you alone, things will always go well: how interesting!
Later on, your foes will get a big laugh out of you.
Of the following two, which one has the better chance
Of remaining self-assured in vicissitude:
The man who has accustomed his mind and magnificent body
To all the luxuries or the man who, content with little,
Fearing the future, provides in time of peace,
As a wise man should, the equipment required for war?
[tr. Palmer Bovie (1959)]

Undoubtedly you believe that for you,
only for you, things will always go well.
And then arrives the day when your enemies
will have the last laugh. In the changeable
events of life, who can count on himself
with greater security? -- he who has
proudly habituated both his body
and his soul to superfluous luxuries,
or he who, content with little, and fearful
of the future, has the wisdom to prepare
himself in peacetime for that which serves in war?
[tr. Alexander (1999)]

Fate won't snicker at you
ever, you must think; what good fun you'll provide
your enemies one of these days. Who will
fare better when his luck changes, one who
coddles mind and body with all comforts,
or one who can get by on little and
prepares for change, the way a wise man
keeps his weapons oiled and sharp in peacetime?
[tr. Matthews (2002)]

For you alone, I suppose, nothing will ever go wrong.
What a whale of a laugh you'll give your enemies! In times of crisis
which of the two will have greater confidence -- the man who has led
his mind and body to expect affluence as of right,
or the man with few needs who is apprehensive of the future
and who in peacetime has wisely made preparations for war?
[tr. Rudd (2005 ed.)]

You alone, is it, trouble won’t touch!
O how your enemies will laugh some day! In times
Of uncertainty who’s more confident? The man
Who’s accustomed a fastidious mind and body
To excess, or the man content with little, wary
Of what’s to come, who wisely in peace prepared for war?
[tr. Kline (2015)]