The idea of choices in Sula has a lot to do with concepts of self-identity and self-determination. The characters who choose certain paths for themselves – who choose to pursue their desires and follow their own ideas about what's right and wrong – often create problems for those around them. But these same characters benefit from a clear sense of self that sustains them through the ups and downs of their lives. Being in control of one's choices is a central theme in the novel, along with the necessity to accept responsibility for them.
The characters in the novel should be free to make their own choices regardless of how they impact the people in their lives. Their main responsibility is to themselves.
Personal choices almost always affect other people. The main characters in Sula fail to see this, and that is their greatest flaw.