Am I too cautious on the road?

I didn't realize this until my passenger mentioned it, but I check my mirrors a lot. I know that's not a bad thing, but checking my mirrors have gotten me into the habit of worrying about other drivers.

When I was driving on the highway with the same passenger, I was backed up on an onramp due to construction. This onramp shared the same lane as the next exit, which was about a quarter mile away. While following heavy traffic down to the exit, I look in my rear and driver side mirror and notice the car riding my bumper. I was visibly frustrated at the person tailgating because even with me initiating my brake early, the person still needed to slam on their brake when we caught up with traffic. It was super uneasy because I try my best to not get rear-ended.

I should mention that I've got about 3 years of driving experience. Am I being too paranoid/cautious about other drivers when I drive? Is anyone else on the same boat?