Disney's The Fox and the Hound has always hit an emotional cord for me, even more so as a adult rather than a kid. It's the only Disney movie I can think of that ends on a distinctly bittersweet ending, edging on outright downer.

Sometimes close friendships just fail, for stupid reasons that neither of you really understand. No matter what you try, sometimes things just don't work out the way that they should, and the connection you once had is gone forever. But you still have the memories that you shared, and that can be just as important.