This is a straightforward one, not requiring any great deal of research. It’s another quote from Jack Kornfield’s Buddha’s Little Instruction Book. This quote’s from page 80. It also sometimes appears in an abbreviated form, as in this tweet:
Be where you are; otherwise you will miss your life. -Buddha
— Live, Love, Inspire (@LoveAdvicePolls) August 20, 2012
Buddha’s Little Instruction Book is not a book of Buddha quotes, as you might think, and as, evidently, a lot of people have thought. As the back cover of the book tells us:
For this small handbook, a well-known American Buddhist and psychologist has distilled and adapted an ancient teaching for the needs of contemporary life. (Emphasis added.)
Unfortunately the title seems inadvertently to have misled many people, and Buddha’s Little Instruction Book is the single largest source of Fake Buddha Quotes on this site.