My view on this subject is strongly influenced by author Caroline Myss. I have been listening to her talk on archetypes and Sacred Contracts here 
*A contract doesn't mean that "all is preordained ". I think of it more like choosing which instrument to play in the Cosmic Jazz Improvisation. Free will has dual aspects: we can be willful, or willing. Again, think about an arena full of musicians. I imagine my middle school bandroom. Some kids would exert their will to blast trumpets and drown everyone else out. (Willfulness that ruined the experience for the rest of us.) Vs. A musician who plays their instrument with sensitivity and willingness to play to the soul of both the compser and the conductor, adjusting volume, timing, and nuance to enhance the entirety of the production (willingness).
Thoughts have been proven to change material reality in the arena of neuroplasticity. Your thoughts materially guide the physical workings of your brain, and vice versa. Thoughts are made manifest by both the architecture of our neurons and by our resultant behavior.*
I hope to gather my thoughts and write more on this topic another time. Until then,
STEEM OM!
(I need to create a badge or emblem for that, my pet phrase here!)