When I was learning to drive the thing that took me by surprise the most is how fast the situation can change. You can take your eyes off the road for a second to check your mirror(s), your speed, etc and just in that tiny bit of time the entire situation on the road ahead of you can change dramatically.

Using a phone while driving is negligence of the highest level. It is so incredibly goddamn dangerous that I would possibly argue it should fall under attempted murder instead.