Seeing a season end.

The postseason is supposed to be a reward. Yet, no one prepares for their season to end, which often leads to tears and shock.
All but one team in each division in the playoffs is going to end its season with a loss.
All of a sudden the work that went into getting this far is temporally forgotten. No one wants to hear what a great year it was.
Yet, when players wake up and reflect, most will realize it was a special season. You've left something for others to follow and build off of.
Those memories will be cherished for the rest of your life. Because while you were playing in the postseason, most had already turned in uniforms.