I started wearing an HR monitor a few years ago, not because I was worried but so I see my effort. That was OK at the time, but now I use it to keep myself from pushing too hard. When I get up around 180 I figure that's enough, and usually my legs thinks so too. But I've hit 190 too, and that was just too high. As long as I recover normally I know I'm OK, and so far that's always been the case. It's hard to let go, but I try to stay under 175 now, and that'll go down over the coming years. I'm 64 now for reference. Oh, and given my age and the numbers I just threw out that calculator just doesn't work for me. What is it? 220 - your age? That would be 156 and that is just a steady tempo pace. I'm no natural athlete either, in fact the opposite.
So when going up a hill I usually go as hard as I can, but if the HR goes over 180 I let up, and the HR always goes over 180 if I push it. On the flats I only would go that high if I sprint and hold it.