Only you can make the decision as to when to hang up the keys. If you are not comfortable driving, maybe it's time. Traffic is moving faster than ever and more cars on the road too. Seems like everyone is in a hurry and slower reaction times really do matter.
I was over the road trucker foe 33 years, no accidents, and have witnessed first hand older unsafe drivers. My dad was also a trucker and the hardest decision he made was to quit driving, but he did when he felt it was time. I am 75 and know my time is coming.