Sometimes the best way to identify a good or bad purchase is to try to put it into words. If you can't justify your purchase with a convincing written statement, maybe your money should stay in your wallet.
You meant to buy a single apple and you came out with a new 4K TV. How did this happen? Impulse buying. We all get the impulse to buy things. If you want to curb the habit, don't even go in the store until you know exactly what you're getting.