This quote is most frequently attributed to Ernest Hemingway. It doesn’t even sound like him. For one thing, that’s about five times as many words as he would have needed to make that point. For another, not a mention of booze in the thing. (I kid, I kid.) (But, like, really though.)
In fact, this quote is by William Saroyan, an Armenian-American writer best known for his Pulitzer-winning play, The Time of Your Life (1939). The “Try to learn to breathe deeply” quote comes from the preface of his 1934 book of short stories, The Daring Young Man on the Flying Trapeze. It was advice to writers, and begins with: “The most solid advice for a writer is this, I think: Try to learn to…” etc.
Hemingway’s version? Probably more along the lines of “Shut up. Have another drink.”