My attention span.
We as a mass of people are losing the ability to be bored. There are some things in life that require a little boredom, so we will lose those as well.
I remember fishing with my grandpa when I was a kid, 4-5 hours of pure boredom sitting in a boat and having to be quiet and not move around. But I learned how to get through it and developed patience, calmness, self-control, things like that.