I've worked through 35 summers with no real problems until I had my second COVID shot.
Shortly afterward and despite being a fit, non-smoking, non-drinking, very active person I had some issues with my heart
These resolved over three or four months and I eventually got back to a decent level of fitness within a year.
Aside from general wear and tear, I'm now not able to effectively regulate my body temperature.
I was ill a number of times over the summer as I seem to get the human equivalent of 'thermal runaway'.
If it's too hot I'm unable to effectively cool down, despite drinking 2-3 litres of water, wearing a hat, factor 50 sun cream and trying to stay in the shade.
Never really liked it too hot but now just can't cope with it.
Did a job on Friday, it was properly cold, which last took me three hours in the summer heat and knocked an hour off.
No problems at all.