If I had my life to live over, I would try to make more mistakes next time. I would relax. I would limber up. I would be sillier than I have been this trip. I know of very few things I would take seriously. I would be crazier. I would be less hygienic. I would take more chances. I would take more trips. I would climb more mountains and swim more rivers. I would burn up more gasoline. I would eat more ice cream and less bran. I would have more actual troubles and fewer imaginary ones.

Don Herold (1889-1966) American humorist, cartoonist, author
“Pick More Daisies,” College Humor magazine (1935)
    (Source)

Also attributed to Nadine Stair, and a Brother Jerome, among others. This essay has gone through a variety of revisions, both by Herold and by a variety of plagiarists. The earliest reference I could find was that cited here, as quoted in The Journal of Health and Physical Education (May 1935) [linked above]. The usual citation is to a revised version of the essay by Herold in "If I Had My Life Over -- I'd Pick More Daisies," Reader's Digest (Oct 1953) (and reprinted in Reader's Digest's How to Live with Life (1965). Benjamin Rossen, "Who Would Pick More Daisies; A study of Plagiarism and Foolery on the Internet" (2000) wrote extensively on the variations and misappropriations of the poem (though he did not know of the 1935 version).