New drivers make mistakes because they lack skill. Experienced drivers make mistakes because they have skill and have quietly stopped applying it. The second category is harder to correct, since every shortcut has been getting away with itself for years.
Rolling Stops
Almost universal, and rationalized by clear sightlines. The problem is that a rolling stop trains you to decide the intersection is empty from a moving vehicle, which is exactly when your ability to detect a cyclist or a small child is worst.
The habit also transfers to intersections where visibility is poor, because it has stopped being a decision.
The Phone
Everyone knows this and a great many people do it anyway, generally with the belief that they are handling it better than others. Reaction times while texting are comparable to significant impairment, and hands-free is less of a solution than it appears, since the distraction is largely cognitive rather than manual.
Glancing at a mounted screen at highway speed covers the length of a football field without your eyes on the road.
Following Too Closely
Confident drivers close gaps because they trust their own reactions. That trust is often justified and entirely beside the point, since a tight gap removes the time you need regardless of how quickly you respond.
Rushed Lane Changes
Mirror without shoulder check, signal simultaneously with the movement, or no signal at all. Modern blind spot monitors have made this worse rather than better, because drivers now delegate the check to a sensor that does not detect everything.
Driving Tired or Angry
Both degrade judgment measurably, and neither is treated with the seriousness of alcohol despite comparable effects on reaction time. A driver who has just had a hard conversation and is now on a highway is impaired in a real sense.
Neglected Maintenance
Tires worn to the marker, brake noise ignored for months, a headlight out for weeks. Each is invisible until the day the margin it was providing turns out to have been needed.
Check tire pressure and tread monthly, replace wipers before they smear, and treat new noises as information rather than annoyance.
Refreshing the fundamentals is not only for beginners. Defensive driving habits covers the underlying discipline, and many insurers discount completing a course.