Boundary theory addresses the balancing of roles that people form with their at-work, and not-at-work selves. This theory focuses on the whole person and what systems work best for them when it comes to creating boundaries with their jobs. SDT looks only at the person at work, and looks at the motivations that people have to complete their work and where these motivations come from. The at-work person undoubtedly affects the person when they leave work, and motivation can come from places outside of work, which is why it is helpful to allow these theories to work together.