Imagine you're running and your shoelace comes undone. Then a friend comes and shouts: "Hey! Stop! Tie your shoe!" Sometimes it feels annoying to have to stop playing, right? But if they hadn't warned you, you'd have tripped and scraped your knee! The friend who warned you (corrected you) saved you from getting hurt.
The Bible says whoever warns us about a mistake is more of a friend than someone who only compliments us and lets us do something silly. Whoever corrects us, loves us!