A sentence crossed out may still have helped the writer discover the one that remains.

Deleted work is not the same as wasted work. The paragraph you cut was how you found out what you actually meant, and the sentence that survives exists because the wrong one was written first and could then be seen clearly. Thinking happens on the page rather than before it. Judging a day’s writing by what is left standing undercounts the part that did the finding.

When you delete a lot, resist calling the session a failure. Write the bad version quickly and on purpose next time, since it is usually the fastest route to the one you keep.