Trying to understand why a ghost-person-baby come back to life does what she does may be quite difficult, but may give a lot of insight as to basic human behavior.
The past seems to influence all of the characters in some way. Denver seems to want to move away from it; it (meaning slavery) was something that she was not a part of. Sethe seems trapped by it, constantly letting it affect her frame of mind. Sethe doesn't want her children to go through what she did. Beloved only seemed to exist in/ because of the past. She died before she was able to experience freedom.
Love is a big part of the book, and the people in it. They are all trapped by, consumed by, moved by, or wary because of it. Beloved can survive as a human only when she is loved, so it causes her to act in certain ways because she craves more and more of it in order to survive. Denver often feels lonely, and Beloved seems to be her only friend, so she (for a while) would do anything for Beloved's love and attention. Sethe "loved too much" causing her to take ownership and caring too much for her children, causing her to go as far as killing them because she thought it would be better.
Freedom, hope for a better life, and survival are also major themes in Beloved. Sethe runs away for a better life, even though it causes her pain and suffering. She sent her children on without her because she wanted them to survive and live a better life than she had had.
