Whenever I go on a trip out of town, I pack extra underwear in case I crap my pants.
Say I'm leaving on Sunday (starting off fully clothed) and coming back on Wednesday, then I need underwear for Monday, Tuesday, and Wednesday, and one extra in case I crap my pants.
Maybe when you are going to get high, you should pack extra underwear in case you crap your pants. You could make a little checklist, "Herb ... check. Pipe ... check. Lighter ... check. Extra undewear in case I crap my pants ... check!"
You might also want a bottle of water, which might help you to not think you crapped your pants when you didn't actaully crap your pants!