You just haven't been there long enough. When I lived in Colorado Springs, I got a friend to come out there... from GA. The first day was OK, the next day we went out and started down the driveway... it was a decent grade down toward the street... all of a sudden he began to walk faster and then really fast, then went headlong into the concrete. Then a couple of days later his lips got all cracked because of the dry air. The altitude can affect you but I was already high, so I didn't notice.
When I was a teen I hiked up in the Tetons to some little lake above the treeline. Then I decided to climb up the steep slope behind the lake, up to the ridge. It was so high and so steep, I had to sit and climb it backwards, sitting down. Icould take three steps and wouldbe out of breath... but when I go to the top it was truly breathless. On the other side of the "ridge" it dropped straight down, looked like at least 1,000 ft. I still have some water from that little lake in a bottle... maybe one day I will get backup there when I get my Scooter Chair!
J