When I was running well and competitively, I often could pass other runners both at the end and during the last quarter of races. I could be dog tired, but I would just push through it. I thought my mental toughness and will to win gave me the edge.
As I aged and slowed up, I was passed at the end and during the last quarter of races. But I pushed myself harder and was more beat up at the end of races than I ever was when I was running fast. My determination and guts were probably greater during the races when my times were slowing.
My point being, when I was fast I thought my edge was my determination and will to win. Most serious racers have that too, there was no edge there. I was just faster, not mentally stronger. I was deluding myself thinking I won because I was mentally tougher.