I regret not buying the Mustang I wanted, instead I bought the "safe" reliable car.... which turned out to be a lemon and I had to trade it in only 2 years later and take a huge finaincial hit on it when I bought the new car. It also turned out to NOT be safe --- many, many blind spots that a Mustang would not have had! :p
I've always done the safe and smart thing. For the most part, I am happy with my choices, but every once in a while I wish I could have just said "Oh what the heck!" and go with the flow.