Is that not accurate? There’s only so many hours in the day, and I have to split them between competing priorities.
If I don’t have time for something, I don’t have the remaining hours to spend on it, given the time I’ll spend doing other things.
If I don’t have time for something, I don’t have the remaining hours to spend on it, given the time I’ll spend doing other things.
So no, you never just have time you're not using anyway. You're always using all of your time. On what is a matter of priorities.
However, if you would spend 19--21 watching a TV series, or twiddling your thumbs, you can choose to take that time to do something else.