You manifest all the time whether you know it or not, you keep attracting people, situations and outcomes based on your inner world.
The inner world includes
your feelings about yourself and the world
your thinking patterns
the very often limited beliefs about what you think you can do
The outer world on the other hand includes everything outside yourself — including all your relationships, how much money you make and so on.
What you manifest or attract in your outer world is determined to a large degree your inner world. So depending on your thoughts, beliefs and feelings about yourself and the world you either limit yourself and attract undesirable things (such as lack) or you manifest what you truly desire.