A friend of mine got kicked off an Olympic team years ago for pot. He went full bore and ended up in jail for dealing heroin. Became a Christian and after his release devoted his life to helping junkies get clean.
I'm not saying pot use always leads to much worse addictions, but its impossible to stay in peak condition with continued use. I had a good friend who was a very good hockey player. He made it to major-junior in Canada, which is the main proving ground for NHL. He was invited to some NHL team summer prospect camps. He smoked pot "recreationally" but often enough. Got injured in a game, gained a bit of weight, got slow. Played a little ECHL professional hockey, but he never stopped smoking and I feel, lost his edge and drive - and that was the end of any professional career