Anyone undergoing ATCO training who has
the idea that each dot will be between 2 and 500+ passengers, and if I screw up they die.
in the back of their mind during normal operations will not normally make it. Their mindset is not conducive to being an ATCO and it would not be good for their mental health.
Sure, when you have an incident, the heart races, but even then you don't walk away and think "200 people could have died there"... until you do it for real and talk to real aircraft you won't know if that's how you will think - there are many people out there who have passed all the simulation training but have failed to validate because once speaking to live aircraft, they just fold.
The training system should be (and in the case of NATS, is) robust enough to filter these people out before they harm themselves or someone else!