It's a loose definition, but "wasting time" means that you're doing stuff which doesn't make you any better (like watching youtube videos only for entertainment / lazyness).
On the other hand, "spending time properly" is somewhat the opposite of that, so it includes a lot of stuff, like self-care (bathing, washing teeth, cleaning your room, etc.), learning (this also includes youtube videos, but only if you're following along!), doing productive stuff (painting, deving, REing, or hell, even collecting stamps (hobby stuff)).
I agree with all you said, Sono. But I wonder, if I do something I enjoy, like listening to music or talking to a friend, is that time really wasted? Even if said activity is not particulary productive?
It depends on what we view as "time spent properly" I guess.
Even time I spend working on a project can be a waste if I get stuck and make no progress, I guess...
I guess it depends on why you're listening to music. If you're going to rate it afterwards (as in, it's a hobby, or you're asked to), then it's time well spent. If you're listening to it as a "time waster" where it's not possible to accelerate time, and you can't do anything productive (long train ride, sitting in a classroom, etc.) then it's DEFINITELY time well spent.
If you're listening to music while doing other things, it depends on what, why, and how. If it negatively affects your performance, then you probably don't even want to do the activity in the first place, so time waster. If it positively affects your performance, then it's time well spent. I can't think of other situations, so I'll assume neutral for those.
As for talking to a friend, if you WANT to, and you ENJOY it, then it's time well spent, regardless of the other situations that could be going on around you.
If you have more important stuff to do, but you only talk to them as a necessity*, then it's most likely a time waster.
*here this means that one side is an emotional wreck, and the other side is being used as an "emotional trash can", but that's a really extreme case. Friends talking is usually almost always enjoyable, so it's "time well spent".
As for the projects (damn, I almost missed that!), even if you make no progress, it's still most likely "time well spent", unless you haven't taken a break in like 6hrs, and you're still focusing on that one shit, well THEN it's an EXTREMELY HUGE time waste! But yeah, if you keep taking breaks, then it's most likely "time well spent".
I learned at my current workplace that sometimes I need to literally just breathe (like LITERALLY DROWNING from the work I'm doing), or very rarely need to play osu (yes, at my workplace) to be able to resolve a nasty problem.
If you don't take regular breaks while working on a nasty problem, you're literally suffocating yourself, and weakening both your body and mind, greatly lowering your chances of figuring out the problem in that state (learned this while working on TWPatcher).
This also applies to everything you're doing which involves more than idle energy use (both physical, and DEFINITELY mental).