Trent, the car and my ability to hold my breath for 45 minutes.

Every time Trent (my son) borrows the car it feels like I put my life on hold until I get a phone call saying he has arrived safely at his destination. Then when the phone rings, I hesitate to answer because I'm scared that it will be someone calling to tell me there is an accident. When does this stop? He is 21, and the facts are he has had his license sine he was 16, but as he does not own a car and lives in the city most of his transportation needs are met by rapid transit. When does this end?