What you described can certainly be a dangerous situation. People don't realize how much of a life or death situation driving really can be, until it happens to them. A semi being involved just makes things infinitely worse. It's never a good thing to harm ourselves, but it's always better than taking it out on someone else. That's just my thoughts, so kudos to you for finding a way to cope without lashing out at others, even though it would be a good idea to try something different for next time. I used to find the same methods as you, but now I usually just scream at the top of my lungs or sometimes beat on my steering wheel (not recommended either).