Sean,

What you've described as "wasting time", we software developers describe as "prototyping". I think that even though you discard the tangible results, the time is far from wasted.
 

That's a good point: you do have to go through the early stages to get to the later stages. You do have to experiment with what works in certain sections, and you probably do have to go down some blind alleys as you shape the plot.

But it's hard to think of it as prototyping when you realise you've just spent days writing something that's no use.

When you prototype software, you've usually got a pretty good idea of the finished product, and reasonable confidence you have the skills to complete it. You rarely prototype features that are completely redundant in the finished product.

When you're writing your first novel, you might not have a clear idea of the shape of the whole plot and might not have confidence that you have the skills to write a novel (since most people start without any training or prior novel-writing experience). You probably will write chapters that you have to delete outright.

That's when people need to accept that they will waste time, because sometimes it'll feel like they are. If people can't accept that some time is wasted, they'll treasure their time too highly to delete scenes that really should go, too.

I think it's easier for people to accept that they'll waste time (or at least, that it will feel like it), than it is for them to think of everything as a positive step towards the final book. With hindsight, it's possible to see everything as progress. But when you're in the middle of a big project, where you have no experience and are unsure you can even finish it, it takes extraordinary confidence to see failed drafts as prototypes.