I'm 60 and get anxious/stressed about everything these days. That's because of years of experience of things going wrong, poor customer service, etc. I now expect the worst case scenario and am sometimes pleasantly surprised when things go well (but it's the minority of times, most of the time things go badly). I spend far too much time on double and treble checking things.
Even with appointments, I phone to check on the morning to make sure it's still going ahead, whether it's a medical appointment, hair-do, booked car test drive, or whatever. Far too many times I've turned up for something to be told it's cancelled. Worst was a 2 hour drive to a different specialist hospital for my OH to see a specialist oncologist - got there with the appointment letter in his hand to be told at the reception that the specialist doesn't work Wednesdays, yet they'd managed to send an appointment letter for a Wednesday. That was an entire wasted day!! Then you get receptionists getting stroppy when you phone at 9am to check an appointment is still going ahead!!
Airports are another kind of hell that I can't be bothered with anymore (Manchester!!). Last time we flied (and it is the last time as we'll not bother again), we left home with plenty of time, some 6 hours before the flight time, allowing 2 hours for the drive (which usually takes an hour), so 4 hours between parking, to get the airport shuttle, check in, go through security, etc. In the event, it took 3 hours to drive there as the motorway was infested with cones (but no workers) for about 40 miles of the trip causing massive congestion, then the car park shuttle bus (should be every 15 minutes) didn't appear for an hour, then horrendous queues to check in, then horrendous queues for security (we'd bought fast track, but even that was queued right back to the check in are) only one scanner open out of a possible 6-8! We literally ran to the departure gate and were the last people on before the doors were closed. Never again!
Basically, we're starting to restrict ourselves to things within our control, as these days whenever you start to rely on other people (even just to do their jobs), it's 50:50 whether they do it or not. We're doing more and more house/garden DIY, more car maintenance, etc., not because we can't afford it, but because it's nigh on impossible to find reliable people to do work for you. We buy most things off Amazon because of the ease in returning faulty stuff and avoiding the battle of wills with a stroppy counter assistant in Currys or Argos!
It's experience of life and all the crap that you get thrown at you which makes you wary and that leads to stress/anxiety.