Sally,

I grew up in this heat and humidity, so I am probably alot more used to it than you would be. It definitely affects me more than it used to, but I do have a stubborn streak sometimes and I am convinced that if i can keep myself acclimated to the heat, I won't reach the point where I just can't function in it.

I definitely listen to my body and back off when I need to, both in the form of slowing down and also stopping to take a break in the shade if necessary. I also always have an extra water bottle specifically to dump over my head if I get too hot.