Zig Ziglar started a thing that didn’t exist prior: motivational speaking. “Power of positivity” family of thought.
Many followed him, doing what he did with their own twists. Norman Vincent Peale was my first. In the 1990s, Tony Robbins had his twist and they continue on under new names like “The Secret”, which is almost identical to Norman Vincent Peale except replacing God with The Universe and is more modernized.
They’re a big money maker in the USA. Business conferences are full of people selling pretty much the same message; Believe in yourself. You can have anything you want if you ask and ask specifically. God/The Universe will provide for your needs if you demand in the right way, etc.
It’s good if you need to get out of a “I can’t do anything right” spot in life.
Cognitive Behavioral Therapy (CBT) is a more scientific way of handling this and it’s shown great progress in helping difficult types of issues.
Earlier versions are Rational Emotive Behavior Therapy (REBT) which I was more familiar with. “I’m OK / Your Ok” pop psychology also fits in this realm.
In the religious realm, “New Thought” comes before even Zig Ziglar, and I suspect was his inspiration but I don’t know enough to say. From 19th Century onwards,
1) God or Infinite Intelligence is “supreme, universal, and everlasting”;
2) divinity dwells within each person, that all people are spiritual beings;
3) “the highest spiritual principle [is] loving one another unconditionally… and teaching and healing one another”; and
4) “our mental states are carried forward into manifestation and become our experience in daily living”.
You’ll see this theme pop up over and over in different places under different names.