Back in high school driver's ed, (around 1979 or so) I was taught IPDE. That stands for Identify, Predict, Decide, Execute. When driving, you should always be looking around, trying to identify potential problems, predict how a problem might unfold, decide what to do about it, then if necessary, execute your plan. If you see a car in your mirror weaving through traffic, you have identified. You can predict he is likely to squeeze in between you and the car ahead, you can decide to make some extra room, make sure you can safely swerve, or merely be ready to hit the brakes. If he does cut you off, you don't waste time figuring out what needs to be done, you already have a plan to execute. With experience, much of this can become automatic--I scan other traffic without conscious effort.
People involved in concealed carry talk a lot about Condition Yellow. This comes from Jeff Cooper's States of Awareness color codes. Condition Yellow is a basic state of awareness-paying enough attention to your surroundings that most threats won't take you completely by surprise. (Short version of Cooper's colors: White, oblivious. Yellow, basic alertness. Orange, paying attention to something specific you may need to deal with, Red, ready to fight.)
There is a good deal of confusion about what Condition Yellow means. I have seen people new to carrying a gun say that they are hanging up their guns, keeping condition yellow all the time is too tiring. They are doing it wrong. Anti-gun people believe it means fearfully scanning for danger all the time like a rabbit. They don't understand it either. Condition Yellow is not limited to those carrying guns. It is not a state of paranoid hyper-vigilance. It is a basic awareness of your surroundings, coupled with the knowledge that you might have to take some action to protect yourself.
It is nothing more than the first step of the IPDE concept learned in Driver's Ed, expanded beyond driving. Simply pay enough attention that you can usually identify situations before they get serious. Defensive carry of a gun involves no more fear, no more alertness than defensive driving.