You know when you make biscuits and you plan to make a certain amount but there's leftover dough...not enough to make a reasonably sized biscuit yet you don't want to chuck it away?
Well sometimes writing can be a bit like that.
I end up having to take out a lot from my chapters, but can't let them disappear and be nothing in a press of the backspace button--so, I save them, name them 'leftover dough' and use them later on. Whether it's later on in the book or used in the rest of the series, every sentence or paragraph of information is relevant and useful. You make use of it one day.
Like an idiot I made a fatal mistake of accidentally deleting over three pages of juicy content written in the POV of one of my characters.
I'm still mourning the loss.
Unfortunately it's just one of those things that still happens. It didn't help that I had several documents open and I was flicking from one page to the next. That's where it helps to have some guidance so you don't get lost.
Another reason why 'leftovers' should be kept aside and not thrown away:
i) Even if you don't end up going back to it later on, it can be used to help rediscover lost inspiration or creativity! You may find that it can push you to continue making more dough until you can make a loaf of bread or a batch of cookies.
ii) It can hold information you completely forgot about.
iii) It could act as a age monitor for your writing. Sometimes you look back at your old work from school and notice just how much you've grown as a writer. You familiarise yourself with your old writing style and compare and maybe decide what you could do better.
The way I see it, hitting the backspace button and deleting a whole batch of information is like throwing away a book or an idea. You've pretty much thrown away something that could have turned out to be a sick creation! BUT it's not so bad when or if the content is gone...because (like me) new ideas keep popping out onto the page and you actually end up writing better than you did before.
There's always a positive to a negative, remember that!