Defensive driving was one of the first thing I learned, before even getting my drivers license, how come others seem to flat out ignore things like that, even for their own safety?
That's just it, why not? I always have the expectation that some unexpected can happen around me in traffic, at any time, and position myself accordingly. If I'm too close to the one in front of me so I can't handle them braking suddenly, then that's telling me I'm too close.
I've been close to a lot of accidents, but never actually in one. Being vigilant at all times when driving and taking breaks when I stop being vigilant, I'm sure have played a huge role in being able to avoid these accidents.
I guess, you're not part of the target audience. :-)
(More seriously, congratulations and many thanks for being a responsible adult.)
Are you seriously avoiding to leave any sort of space in front of you just because other cars might go into that space? Seems like a dangerous game to play not just for yourself, but for others too.