Being hunted is not very much fun. It is easy to remember the horrible glance backwards from a nightmare or an intense thriller movie. The horror creates a feeling that drains confidence and creates panic.
In the men’s 200 fly the reigning champion Kristof Milak was almost a body length ahead with 50m to go. He set off on his last length but all was not right in his head and the winner of the 400im Leon Marchand was in second place.

Milak had spent quite a lot of time out of the pool, if reports are correct, and had got back only at the insistence of his coach. He had a fly in the mental ointment.
So this mindset, any challenge might be worrying. With only 25m to go (probably 23m) he did the worst thing he could do; he glanced backwards. That is counterproductive to a winning mindset, it is not a physical draining thing but is mentally draining.
In this photo (below) it might not be obvious but in the previous breaths Milak was looking straight forwards, in this breath he has turned slightly to see where Marchand is (you can see his black swim cap as he starts his next stroke). Also on the 150 turn he would have seen he was a body length ahead…now Marchand was at his hips, he was catching up!

I’ve often watched swim races where the athlete raced from the front and crumbled as swimmers attacked from behind on the last 50m of the 200. The mindset at that moment of looking switched from hunter of an Olympic gold, to the hunted.
When you look backwards your focus is on a potentially destructive idea that is almost unavoidable. Someone (or something) is chasing you and may catch you. This destructive idea is another form of suggestion. It creates panic.
Suggestion is the bread and butter of advertising. I’d go out on a limb and say advertising is a trillion dollar business. It is ubiquitous (yes my favourite word). A thought, or just a slight suggestion, created by your own mind through suggestion, is a way to turn your mind on an outcome that you might not want. We all drink Coka Cola because Santa does.
The idea in the pool, to look backwards, to see where your competition is, changes your focus on your perfect stroke, your plan for the final stage of the race, and now becomes ‘I can’t lose’. However your mind doesn’t work in positives or negatives, or ‘can’ or ‘can’t’. It work in ideas, or pictures. The idea behind I can not lose, is: I can lose.
We are human. You aware of your surroundings and you have an innate inherited fear of being hunted. Mammals are food to most of the carnivores of our world. We are always absorbing our world through our senses and as soon as something important is sensed we react.
Being fearful can be useful. You must be firstly be humble enough to know that you can be hunted. Then you can prepare for it and not panic. A glance backwards at a hunter you didn’t know was there, is very scary indeed, because they may get you! Especially if they are a swimmer from France swimming in a French Olympic stadium with the endurance of a 400im swimmer.
(Side note: congratulations all swimmers in the 200fly final, it is a wonderful achievement and to Ilya Kharun for a podium performance for Canada in 200 fly. Canadians have been close-but-not-quite for a long time!)