The body can intoxicate itself. If you refuse to drive after smoking a bit of weed, remember not to smoke after jogging, experiencing any emotion, after sleeping too much, and many other situations which everyone has no problem driving in.

Driving comes naturally after a while. Unless your motor skills are impaired or your reaction time slowed (as it could be by depression, being tired, drunk, or too stoned) then driving comes second nature to most people even in various mindsets.