Alternative Character Interpretation: Was the Postman crying at the end because he was defeated or were they Tears of Joy? If you look below, one of his reasons for hating Christmas was being put on the naughty list, so it's possible that he was touched that the penguins gave him a gift, even if it was raw fish.
Olive wants to save Christmas despite people, the weather, and bad luck impeding her quest. Viewers can't help but feel sorry for her when she almost feels like giving up.
Jerkass Woobie: The Postman. The reason he hates the Christmas season is because it greatly adds to his workload. People who have to consistently work during Christmas can probably sympathize with him. Although, it is implied that the true reason is because he's mad at Santa for putting him on the naughty list.