Here is a simple test. I took it myself many years ago, that time with respect to LSD. The problem was that all the wonderful, oh so deeply thoughtful insights would flee as soon as the drug wore off.
So I resolved to try and preserve them. Before they might flee the very next time I wrote them down. Reading them afterward was most disappointing.
Likewise so with marijuana. It has been quite some while but I very recall just how many hours I spent watching re-runs of "I Dream of Jeanie" and other such TV pablum. How low must have my discrimination have sunk in any such case as to have devoted uncounted hours from the fleeting moments of my life in this pursuit?
Let me suggest an experiment. Pollute the bloodstream however you wish on alternate practice days, just be consistent on which days those shall be and do it where the MA instructor can observe. Then ask, "Sensei, how does my performance compare on Thursdays versus Tuesdays (or whatever)."
To sum up, you CANNOT judge your own performance while your own judgment is impaired.
Gan Uesli Starling
Kalamazoo MI USA
PS - Personally I would not outlaw drugs any more than I'd outlaw bungie jumping or any other such foolish hobbie. But PLEASE, don't go ascribing physical, mental, nor especially any spiritual benefit to their use.