This exercise is to show how the metaphysical reality, the reality of thoughts, affect the physical reality. The responses you will get, if you are able to concentrate enough, will be immediate.
Try thinking of something that left or leaves you feeling less, feeling hurt, alone, fearful. A memory, a worried thought of the future. Try feeling how your body reacts. (The beneficial side-effects of this exercise is that it also starts to heal some of our wounds, because we begin to move through them. Instead of trying to move around them.)
Then, try to do the same with a positive thought. Something nice somebody said or an unexpected gift you were given. Try noticing how your body reacts.
Note the difference in bodily responses to each separate thought; a “negative” versus a “positive”.
It’s really interesting!
This is a good exercise for spring-cleaning your inner space. =)