I live in Utah. There are many mountains. More specifically, there is THIS mountain:

This is Timpanogos. It is likely the most-hiked mountain of Utah Valley, probably the most-hiked in the world*.
*Not true
The first time I ever hiked Timpanogos wasn’t just exhausting: I was completely depleted of any life form that might have existed inside me.
We made many mistakes, most of them mine, given how much of a novice I was. I was taking a spinning class at the time and thought that I had the cardio for this hike, but OH HO HO how wrong I was.
We hiked sometime in July, I think, and we started at 10 am which is like the worst time ever to start a hike. In July. With the hike starting at an elevation of 7,370 feet and going up to 11,752 feet. And given that the trail is approximately 7 miles one way, even the most inexperienced of hikers (i.e. me) can complete the journey in 8 miserable hours.
There were many tears. Also some sunburn. And a lot of squatting on the trail to pee (and accidental mooning) to compensate for all the water I drank.
When you gain elevation, the air gets thinner. Pretty simple. And when your cardio experience is equal to, I don’t know, a spin class you attend 3 times a week but that’s literally all the exercise you get, then you WILL be gasping for air worse than a trout on on a hook.
The worst thing about summiting a mountain is that when you reach the top (which I didn’t this time, I was approximately 500 feet from the top and I just couldn’t handle it anymore, it was so windy and cold and I was in a thin t-shirt and sobbing hysterically) you have the get back down. As excellent a helicopter ride off would be, not one of us is Warren Buffet and we have to go back the way we came.
And when you’ve hit hiking for about 7 hours you’re ready to be off this HORRIBLE MOUNTAIN.
Austin asked me if I would ever do that hike again and my reaction was more or less like this:
And then I did it again the next year.