What is one possible theme of the giving tree

Self-Sacrifice and Love could be possible themes of the story "The giving tree". The story shows that to make people that you love happy you may need to give something up which is important to you. The Giving Tree would be a touchy-feely story full of kindness and generosity. There's definitely kindness and generosity to be found in the story, but it's pretty one-sided. Sure, in the beginning, the tree loves the boy and the boy loves the tree, but things go kind of sideways from there. The boy doesn't always treat the tree well, but never the less the tree continues to love and give to the boy in order to keep him happy.