Ambitious Men cheat themselves, when they fix upon any Ends for their Ambition; those Ends, when they are attained to, are converted into Means, subordinate to something farther.

François VI, duc de La Rochefoucauld (1613-1680) French epigrammatist, memoirist, noble

Réflexions ou sentences et maximes morales [Reflections; or Sentences and Moral Maxims] (1665-1678) [tr. Stanhope (1694), Part 4, ¶65]
    (Source)

Reported in multiple translations, but no modern ones. I cannot find the analog for it, the French original, or the "official" number.

Appears in the 1706 (Powell) ed. of Stanhope as ¶711.

Alternate translations:

The ambitious deceive themselves in proposing an end to their ambition; for that end, when attained, becomes a means.
[pub. Donaldson (1783), ¶32]

When the ambitious propose an end to their ambition, they deceive themselves; for, when attained, the end becomes a mean.
[ed. Carville (1835), ¶29]