Most anti thing I ever did, besides financing a car I wanted, rather than needed over 5 years, was continuing to drive the car after my job generously allowed me to use a company car. It was a 2 door Ford Explorer, not very nice to drive, but still free. Later it was upgraded to a GMC Envoy. I was living in Las Vegas at the time, and some of my friends and I would hang out at this bar after work. I usually played a little video poker (getting my drinks comped) and one day hit a $4k royal flush. I used it to pay of my car a year early, but I kept driving it. Later my work upgraded my company car to a brand new 2012 explorer. Did I mention they paid for the insurance, gas, and maintenance? And they paid people to come us at work, to wash it and change the oil. All I was responsible for was paying a federal tax on the benefit. This cost per year would have comparable to what I was paying for minimum insurance coverage plus $1000 deductible comprehensive. This tax was based on me having the car 5 days per week, even though I was welcome to use it 24/7, as long as I didn't abuse the privilege.
So basically, I could have had a nearly free car for the last 5 years, but I didn't bother because I liked having my own car. I'm now starting a new job in Ohio, but I never factored in the company car I gave up when making my decision to leave Las Vegas. After adding everything up, (taxes, rent, car, etc.) my total compensation was probably more in Las Vegas. This car is worth $7,500 at most now. At least it's paid off, and has had only one unscheduled maintenance issue. Looking forward, I will be biking to work as much as possible.
I can't understate how much that car purchase cost me. Back in 2007, I could have kept my dented and cheap, but mechanically perfect 97 civic. But I bought a used (but still overpriced) 05 Altima with an added on bs warranty! I believe that single purchase coupled with not taking advantage of a huge work benefit, has delayed my FI by a full year at minimum, maybe two. It really is a case of your money or your life.