...talk with him on the way home about what it means to be a man, when it comes to fandom. It means we suffer. Suffering as a fan is noble. It is necessary. Sometimes, it can be exquisite. There is no pleasure without pain in life. It's time he starts to learn disappointment!
Maybe introduce him to at least the general concept of sadism and self-flagellation. He is going to need to understand it to be a fan. You might as well get him started early.
Explain that starting every season, knowing you're about to invest hundreds of hours desperately hoping for something you basically know up front is never going to happen is not foolhardy. No! It's how we prove our worth as fans! It puts hair on our chests - figuratively-speaking, of course.
And then tell him the greatest part: that one time, when it all works out - when your team achieves what you have always dreamed about - you absolutely CANNOT allow yourself to enjoy it. It is at that moment that you must begin mentally preparing yourself for the reality that more suffering is but a short moment away. Because winning back-to-back is nearly impossible.
Man, it all makes so much sense to me! How could anyone not logically love being a sports fan?