A dictionary of Proverbs (Oxford Paperback Reference)

You cannot make an OMELETTE without breaking eggs
Cf. Fr. on ne fait pas d’omelette sans casser des a’ufs, one does not make an omelette without breaking eggs.

• 
  1859 T. P. THOMPSON Audi Alteram Partem II. xc. We are walking upon eggs and.. the omelet will not be made without the breaking of some. 1897 R. L. STEVENSON St. Ives viii. You cannot make an omelette without breaking eggs,.. and it is no bagatelle to escape from Edinburgh Castle. One of us, I think, was even killed. 1974 J. MANN Sticking Place iv. ‘In your philosophy, it seems that some men have no right to live at all.’.. ‘You can’t make an omelette without breaking eggs, Mother.’ 2000 National Review 20 Mar. 22 Nor should anyone be satisfied with the argument that eggs must be broken to make an omelet—the idea, in other words, that effective law enforcement requires the occasional slaying of an innocent citizen. ■ pragmatism; ways and means
  

ONCE a—, always a—
This formula produces a limitless variety of proverbs, many of them depreciatory. Some are of long standing, while others appear to be one-offs. A small selection of sayings in this form is illustrated below and in the next two entries.
1622 J. MABBE tr. Aleman’s Guzman I.I. i. Once a knaue, and euer a knaue:.. For he that hath once beene naught, is presumed to bee so still.. not considering.. whether.. hee had reformed his manners or no. 1655 T. FULLER Church Hist. Britain VII. xxviii. Latimer by the courtesie of England (once a bishop, and ever a bishop) was in civility saluted Lord. 1706 J. STEVENS Spanish & English Dict. s.v. Hurtar, Once a Thief, always a Thief. 1820 M. EDGEWORTH Letter 15 Nov. in Maria Edgeworth in France & Switzerland (1979) 277 She loses her rank.. by marrying one of inferior rank. . . French and Russians are with reason surprised with the superior gallantry of our customs which say once a Lady and always a lady. 1953 R. CHANDLER Long Good-bye xliv. I went out of the door and got out of the building fast. Once a patsy [dupe], always a patsy. 2002 Times 2 21 May 6 Yet although lapsed Catholics may rebel on the surface, they cannot escape the Once a Catholic, Always a Catholic dictum. ^constancy and inconstancy; human nature