I danced with freight for almost 2,000 hours before I put my foot down one night and said nu-uh not going. It was a particalarly lovely +FZRA night at Hopkins and myself and Van pilot from (let's call them Mom and Pop to protect the crummy company's identity). I fired up a Baron and it immediately started to spin in place on the ramp while I shut the engine back down. I said "hecks no", stepped out of the airplane and promptly fell on my butt.
After looking around to see how many people were laughing at me, I went inside and called the company and informed them of the indefinite delay. The Caravan driver was doing the same (keep in mind heavy freezing rain was falling). My phone call was 30 seconds, and the company said well that sucks but we understand. Mom and Pop Van operator started laying all sorts of lines down on the pilot, over multiple phone calls, and finally summoned him to drive into HQ, about an hour or so away (hope I didn't give away too much info there) on one of the crappiest winter nights that I have on memory. He drove. I waited, and finally took off about 6 hours late after things cleared off a bit. The entire experience made me extermely grateful to work for a company that respected your decision to say no, and not for those people over at...well nevermind.
The only other thing I'd say is if you haven't ever had the opportunity to say "NO", when that night comes it will likely be pretty obvious. Fly safe guys and gals.