How much power do thoughts have?

Please note that I am not interested in discussing the rather obvious fact that our thoughts dictate our actions. I want to discuss the direct impact of our thoughts.

How relevant are our thoughts? In what ways do our thoughts impact the physical world? Here are some examples:

Does having good intentions make you a good person, even if you don’t take action?
In what ways do our thoughts impact our bodies or our physical health?
Do you believe that your thoughts or mindset have any “power” to affect outcomes – for instance, does optimism really stack the deck in your favor?
Feel welcome to discuss any other thought-related topics.