olivesmarch4th, now that you’ve got the ‘distance to the next car’ settled, the next thing I would recommend (since I don’t know if you do this already) is to look further down the road.
A lot of people that I know for whom driving causes anxiety are watching the cars right in front of them. They feel constantly under, well not ‘attack’ exactly, but you know what I mean. Because they can’t predict the changes in traffic flow from one moment to the next.
But now that you’ve got enough stopping room in front of you, you’ve got a little time.
Work towards focusing on the cars much farther in front of you. I’d guess I usually watch at least a quarter-mile out, more if I’ve got the view for it. You might not feel comfortable with that distance at first, but work towards it.
Watch all of the traffic in between with your peripheral vision. (Again, it’s not exactly peripheral, but it’s similar.) You can see enough of those in-between cars without actually focusing on them to catch problems. When you see something that ‘alerts’ you (e.g., brake lights flashing, cars swerving, etc.) in those in-between cars, you can refocus your attention there.
Doing this gives you a much earlier warning of many traffic problems ahead, so that you can have more control and more options, and you frequently have time to deal with them less drastically. For instance, I can often just slow down a bit (lifting my foot off the gas) rather than having to hit the brakes to avoid a slowdown in front of me.
This is not only less stressful (it can even become a bit of a game!), it actually improves traffic flow behind you. (Well, right up to the next idiot riding someone’s tail, anyway.)