Thanks for posting this - I used to believe it was all as evolutionary theory told us: you had genes and either they helped you survive or not.
Now, I've come to understand exactly this - the dynamic is much more complex. Our perception of a stressor impacts how our body reacts. And our reaction - positive excitement to take on the challenge - or doubt and panic - also sends signals.
Our genes react to our body's chemistry in how they are activated and - as we've learned about mutations - every stressor can become a mutagen as well. Making our genes change with how the stressor impacts the body.