The trusting innocence of your passenger. How tempting to show off your skill! I managed to persuade many friends and family to come with me in a glider, and did my best to be careful and responsible, and only once did one of my pax need a barf bag..... Don't forget, however, to have one handy.
Basic rule, never be ashamed to turn back if weather looks dodgy. Once, halfway there, had to rent a car in Texas to reach our destination. I had consulted with the latest forecast from Flight Service....said my passenger, "Couldn't you get another opinion?"
RVR in Austin about 500 feet. No thanks.