Your thoughts and energy create your reality.
Each thought we have creates an energy flow within and around our physical being.
This energy attracts its likeness.
So if you're thinking, "I'm lousy", then your energy kinda, well, lousy - and you attract lousy experiences.
The opposite experience occurs when you think high-level thoughts like, "I'm great!"
When you think and feel, "I'm great", you exude an energy of confidence and in turn attract great experiences into your life.
Each thought you have informs your energy, and your energy manifests into your experiences...
If you truly want to use your energetic power to manifest greatness, you must clear all that blocks you from believing in your greatness.