By nature, I'm a very defensive person, which translates to my driving as a very defensive driver and someone that never tailgates, which is one of the most dangerous conditions out on the roadways, along with speeding.
I don't think my cycling, which is my primary form of transportation, affects my defensive driving skills one way or the other. However, I do think my excessive time on the bike does make me a more patient driver, which helps me keep the speed down and my distance away from other motorists; so in that sense, it does improve my driving.
I'm always struck when I take my foot off the gas pedal when I see a red light up ahead, there are a ton of vehicles that speed by me, including cars that change lanes from behind me, just to get to the light a few seconds before me