Thoughts can also create emotional feelings as well, and thus we may want to control our thoughts even if we don't care so much about changing our external outcomes. The constant worrier may have a nagging voice in her head that says her success never counts.

The importance of thoughts and beliefs ranges depending on whom you ask. For some, beliefs have mystical powers that transcend a physically justifiable version of reality. To believe something is, in a certain sense, to literally make it true. Others reject the supernatural, but argue that beliefs still highly constrain our attention, making self-fulfilling prophecies frequent. On the opposite extreme are those that argue for a mostly passive role of beliefs, recording the world but not much changing outcomes. To those people, having true beliefs matters more than believing things to make them true. Regardless of where you sit in this spectrum, the content of our thoughts and beliefs is central to self-improvement.