Do what you can, with what you’ve got, where you are.

Theodore Roosevelt (1858-1919) US President (1901-1909)

An Autobiography, ch. 9 “Outdoors and Indoors” (1913)

Variants:

• "Do what you can where you are with what you've got."
• "Do what you can, with what you have, where you are."

Actually attributed by Roosevelt to "Squire Bill Widener, of Widener's Valley, Virginia" as one's "duty in life," but usually misattributed directly to Roosevelt.