I did not then believe, and I do not now believe, that any man should ever attempt to make politics his only career. It is a dreadful misfortune for a man to grow to feel that his whole livelihood and whole happiness depend upon his staying in office. Such a feeling prevents him from being of real service to the people while in office, and always puts him under the heaviest strain of pressure to barter his convictions for the sake of holding office. A man should have some other occupation — I had several other occupations — to which he can resort if at any time he is thrown out of office, or if at any time he finds it necessary to choose a course which will probably result in his being thrown out, unless he is willing to stay in at cost to his conscience.

Theodore Roosevelt (1858–1919) American politician, statesman, conservationist, writer; US President (1901–09)

Autobiography, ch. 3 “Practical Politics” (1913)
    (Source)