The sunk cost fallacy only applies when you can see the likely outcome is no longer beneficial and continue anyway.

“ Has the athlete who trained 7 years to get to elite status wasted her time, or is she on the brink of a series of pb’s that will rocket her into contention for gold, two months out from the olympics? It’s hard to tell.”

This is not a sunk cost fallacy. You need to make a follow through even though you know its a loosing proposition. The training is a sunk cost, but the fallacy is making a decision based on that sunk cost.