Nonduality is an Indian philosophy that was written in the Upanishads (8th-6th centuries BC.) It points to the idea that everything is one energy at play and everything goes as it goes. You, as a body-mind system, are an instrument being played by energy. Our idea of being an individual with free will, is merely an illusion created by our brain.
Planets are circling around in the universe, the wind blows, the tree grows and you are reading this text. It all goes automatically. Because a human being has self-awareness, we see ourselves as a separate individual. This idea is creating a lot of worries and frustration. We are continuously trying to maintain our self-image and we live with fear for what might happen in the future and frustration about things that happened in the past. However, life is much easier than you think, but harder when you think.