I understand the whole "Tension" angle you are talking about, I sometimes do better also when I don't think about playing and just relax.

I do not get high or drink before I play because it ruins my concentration and learning guitar is hard enough without being stoned or or drunk top of it.

With that said, I am legal to buy and use medical marijuana in the state where I live. I am 64 yrs old, employed in a technical position and have smoked on and off since I was 14. I have never been addicted to weed or any other drug even though at one point I was smoking an ounce of high grade Columbian a week. Soon after doing that, I moved into a job using heavy equipment and voluntarily quit using weed cold with no after effects. I am coming to the end of a career filled with high tech thinking and one that was monetarily very lucrative, so no.. weed did not damage my brain.

I do not advocate anyone using drugs, and I do not want to make waves here, but at least one of these posts was kind of like listening to the war on drugs speeches of the seventies to me.