^^^ But some people have no problem with it. I taught a DoD level 3 defensive driving course while high every day. I also do math better when properly buzzed. Marijuana affects different people in different ways.
The amount, and regularity of usage, also determines how it affects your behavior. I know people who smoke every day, the good stuff (no really, the GOOD stuff), and it barely affects them because they have built up such a tolerance, as I'm sure you have. Others, who only occasionally smoke can get wasted off a couple puffs. Not much different than functioning alcoholics that get up in the morning and start drinking, and you'd never know it because they have built up such a high tolerance. What Ward's tolerance level was is unknown.