Most people have both a higher and a lower self.
Throughout our lives we shift back and forth from one to the other of the two selfs. With our self-help practices and disciplines we strive to stay in the higher self longer.
There are quite a number of reasons why the higher and lower selfs will separate from each other. Some might argue that we are born with only a higher self and that the lower self is developed because of activities that happen throughout our lives.
Some will say that we come into this world with karma. I believe that the only karma that we have to deal with in this lifetime is this lifetime itself. I think it's difficult or perhaps impossible to ascertain the certainty of previous lifetimes or lifetimes beyond this one. Rather than debate such issues, I think it's more practical to stay in the present moment and deal with the causes and effects pertinent to this lifetime. If you master that, you'll be pretty awake and you'll feel pretty good.
When you're in your lower self you can find your way back to your higher self. Meditation is the best way to do so. When you’re relaxed and focused on the present moment, you're better equipped to respond as your higher self’s dictates.