There is a relationship between thoughts, emotions and the physical world. As a species we are still at a point where we are trying to come to a common understanding of the nature of our own beings, of everything else around us and how everything is related to everything else. There is a big debate about it all. It is all up for grabs and we can all take part in that debate.
Scientific theory now supports the idea that everything is energy vibrating at different frequencies. Light is energy. The physical body, emotions and thoughts are all energy. As something occurs at one frequency of energy there will be a corresponding activity at all other frequencies. This is how all those things like affirmation, visualisation, success imagery, goal setting and having a positive mental attitude work. Everything is connected. This is why when we change our minds things actually change in the material world. We know this. We witness this.
Everything is connected so everything matters. Everything we do, say and think matters. The choices we make matter. Who we choose to be matters. What we do affects what happens, so we can affect what happens by what we choose to do. If we choose to think about something fantastic, at the very least it keeps us out of anxiety and so changes the chemical composition of the body. At best it may well help us to manifest a more fantastic reality in the next moment because the next moment emerges out of this one.