Losing to someone younger stings. Learning from them stings less than losing to them again.

The sting is about rank, not about the game. Your mind wants to explain the result away, because accepting it means accepting that they did something better, and their age makes that harder to swallow. The trouble is that the explanation does nothing about the next match, while the thing they do better is sitting there available to copy.

Watch what they actually do rather than how you feel about them. Pick one habit, one shot, one bit of positioning, and ask about it or simply take it. Now you have the thing instead of the grudge.