As a late-onset and not very good triathlete, I can verify that the picture on the right is not useful as a goal to aspire to. Yes, some things in life work like the picture on the right. But, as you say, the picture on the left is far more common and usually it's not our choice, as others have pointed out.

If there's a lesson, it's to encourage the person on the left. Are they frustrated? It appears so. Have they given up? Clearly not. Maybe they need to change their plan of attack. Maybe they can get some help. But it's more admirable in my opinion to persist in the face of adversity than when your efforts are consistently rewarded.