Obviously, you are not one of those idiots that would text and drive, but anxiety and hesitation can cause just as many accidents. Perhaps a driving class with actual on the road training would do some good.
As far as Highways go, most young people I have talked to have had problems with merging, people tailgating and being passed by trucks and other cars.
The biggest problem I see every day is people going too slow in the wrong lanes. This usually happens because some idiot told them to stay 5 - 10 mph under the speed limit to be safe. Not true! The safest speed is matching the general speed of those around you. You don't want to be the fastest or the slowest. Just keep it in between.
As for merging, match your speed to the traffic you are joining and do your best to time it right. Rule of thumb when in traffic and two lanes are merging without a yield, if the other cars front bumper is ahead of yours, they should merge in front of you and the same for you being in front of them. Remember, it's easier for someone to slow down than it is to speed up.
Tailgating, well, we have all seen that jackass out there trying to get there 1 minute faster by risking multiple lives. Not much you can do about him except get out of his way and let him go on to the next person. Sometimes, people don't realize they are too close and a gentle tap on the brakes just to get your lights to flash for a second is enough to wake them up and get them to back off. Another trick is to wash your windshield. The over spray will also hit their windshield and snap them out of it.
Other than that, use your signals and mirrors. Don't signal miles ahead of your turn because people start to think you don't know it's on and ignore your intentions, but don't turn them on at the last second either.
All in all, it's all just practice and learning how to read other drivers. I'm from NJ. driving amongst idiots is the first thing we learn.