Driving Instructor I"m Not!

My recently turned 18 year old son passed his driving test on his first attempt back in July this year, 2015. Let me tell you the responsibilities for me in the year leading up to this event were not my favourite. Now as the mother and sole parent, I know I have many roles to play and many responsibilities to fulfill, I'm up for the challenges, that's why I chose to become a mum! However; one challenge I don't care for, is the one of Driving Instructor. I admit, I feel I did a good job, was fairly patient, not too cautious or nervous......at least I didn't show it, didn't want to make my son nervous because I was! I have to admit he did a pretty good job, didn't make too many errors.
Hours and hours were spent with him in the driver’s seat while I couldn't take my eye off the road around us, while watching out for the idiot drivers. I made sure I drilled it into his head...... 'always, assume that others are going to make mistakes!' For the most part he was good, couple of times he surprised me by expertly avoiding near collisions, which were the fault of the other drivers. One day though, while teaching him how to use the drive through at Tim Hortons, we know how important this is, he drove up to the window and realized he couldn't reach the window to pay and collect his order. So he undid his seat belt and reached over, at which time I heard the car engine rev so high. It was one of those instant adrenaline rushes that are upon you in the blink of an eye. As he reached over his foot depressed the gas pedal to the floor. Thank goodness he had placed the gear in park.......thank goodness I had taught him to do this......otherwise we would have taken out the gas pump at the Esso station about 15 feet in front of us! It's through those near collisions we learn from our mistakes......gosh I hate those moments!
One of the things he always had to be reminded of was to check for pedestrians while making a right or left turn. Every single time he would be so focused on the traffic that he totally forgot about pedestrians. Part of the problem being though that not many are generally crossing the road as most of us drive or take the bus, unless you are around a school when it's start or finish time. The majority of the time there were no pedestrians, but he has to remember to double check because all it takes is one time! The other problem I had with his driving was that he didn't slow down early enough. So I drilled into his head when he sees the brake lights ahead go on, get his foot over his brakes and slow down. Eventually he got better and always left a good space between himself and the car ahead, but I notice now he's back to his old ways!
So two weeks ago we were going an hour away to visit family and he had mentioned driving on the highway. Oh lord.....did I have the nerve to attempt that? Well I did and was a nervous wreck. It was Thanksgiving weekend, everyone and their neighbour were on the highway. There were accidents and construction everywhere. If I told him to slow down or stop once, I told him a thousand times. "Mum, relax, your such a back seat driver" he said to me.....ouch! We made it safely to Oakville but he hasn't driven much with me in the car since. He told me he isn't going to as I criticize him too much when he's driving. This brought back memories of when his dad was my passenger in the car. He would stretch his feet out to the imaginary pedals and grab the dash board like I was flying an airplane or something. How did that help me? It didn't, it made me a nervous wreck to the point that I stopped driving if he was in the car.
So my thought about this is when and how do you stop being the driving instructor after being it for a year, especially now that my 16 year old has her G1 and is starting to learn of course with me in the passenger seat. Lord Help me please!