Manifestation is your proactive application of the Law of Attraction, one of 12 Universal Laws that govern our lives. According to Wikipedia, the Law of Attraction brings to each person the conditions and experiences that they predominantly think about, or which they desire or expect. Simply put, the Law of Attraction is like attracts like. The universe returns to you whatever you think about the most.
For example, if most of your mental energy is focused on how people mistreat you then you will attract people who mistreat you. Stated another way, if you constantly beat yourself up for being less than perfect, rich, smart, etc., then people in your life will tend to demean and disrespect you.
Such negative manifestation of your predominant thoughts and focus of your mental energy isn’t about punishing you nor is it about you being unlovable or unworthy. The Law of Attraction operates without judgement. It does not care if you are a doctor, parent, janitor, teacher, salesperson, server, billionaire, etc. The Law of Attraction is the same for all humans and manifests what you focus on the most.