As with any other activity, experience brings increased comfort. As a rookie, you're pretty much nervous about everything. As time passes and experience teaches important lessons, you learn little things that both ease anxiety and allow you to read a given situation better.
After 20 years, I can honestly say that a "routine traffic stop" really isn't very worrisome. However, I am always aware of the possibility that things can go sideways quicker than you can react. There is only one occasion in which I have been shot at during a traffic stop, but multiple times when people have either tried to run me over, or simply been nervous themselves and forgot to put their car in park or some other silliness. Runners and fighters are probably the next two most common actions, in that order.
The most common conflict type is verbal. Turns out, people in general, don't like to get pulled over, and unpleasant people REALLY don't like it. I can usually tell how the conversation is going to go before I arrive at their window. Most often, the worst case is that someone gets a ticket and is maybe in a bad mood for a bit. Sometimes, I get to hear the most outrageous and implausible stories you have ever heard about why someone was doing whatever it is they were doing. I should probably write a book some day. Truly funny stuff!
In my twenty years, I have worked every shift, and every part of the city. The quiet suburbs, the inner city, high crime neighborhoods, traffic enforcement, and SWAT. My time is currently split between being a "Wheels" instructor (motorcycle) for out traffic unit and as a field training officer for newly commissioned rookies. I have seen both the good and the bad of the job, and couldn't imagine doing anything else. I love my community and my role in it.
JW