Why can't we just tell our brain to produce happy chemicals without forcing it through reaction to drugs/good events?
At what point does automation end and human consciousness begin? Why can we think before deciding to do some things but not everything?

I'm not saying that the soul is real and separate from the mind/body, but... I mean, what's the biological and evolutionary reason why we can decide certain things but have zero control over others?

Meditation is also very powerful despite literally being nothing but thinking quietly. What's the biological/chemical explanation for this?