Nobody wins a 5K in the first four hundred meters. Plenty of people lose it there.

An early burst cannot win a long effort, though it can certainly lose one. Going out too hard buys a position you cannot hold and a cost you keep paying for the rest of the distance, while the people who started sensibly are still intact where it matters. The first stretch is about not wrecking yourself.

At the start of anything long, deliberately go slower than you feel like going. Save the urgency for the part that changes the outcome. The discipline is in tolerating being passed early by people who will not finish ahead of you.