cart before the horse, don't put/set the

proverb Don't do things preemptively or out of the proper order; don't get ahead of yourself. Don't put the cart before the horse and pick out your dream car before you have any money saved up for a down payment. A: "I've got a few ideas of in-app purchases we can implement." B: "Whoa, whoa, don't put the cart before the horse. Let's focus on actually finishing the app first."

Prov. Do not do things in the wrong order. (This can imply that the person you are addressing is impatient.) Tune the guitar first, then play it. Don't put the cart before the horse.

Don’t reverse the natural order of things. This expression no doubt dates from the time when horses first were used to draw wheeled vehicles, and began to be transferred to other affairs almost immediately. Cicero accused Homer of doing so, complaining that the Greek poet stated the moral of a story before telling the story. From the 1500s on, numerous English writers—Sir Thomas More, William Shakespeare, Charles Kingsley, to mention just a few—used this turn of phrase, which also appears in Greek, Latin, French, German, and Italian. In English it was a cliché by the 1700s.