At every point in my life after age 25 or so, I could look back 10 years and be appalled at how much time I wasted back then. 50-year-old me is angry at 40-year-old me for wasting my 40s, as 25-year-old me was angry at 15-year-old me for wasting my high school time. What a waste my youth always seems!
I generally tend to not have that feeling.
For me to feel like it is wasted is to put on a definition of the time period that wasn't there. It is internal personal fan fiction at that point.
I don't feel like I missed out on anything.
There is also the added point of whatever position you take, it is always a trade off with something else.
To be awfully reductionist. The fat people envy the skinny because their health is in check, the skinny envy the fat because they have a sense of care free freedom.