I don't know, this is good advice perhaps for things which are not important.
But, if you are writing an email to a person whose time is valuable, better not to do it quickly. Save a draft, come back to it tomorrow, read again, then send.
If you are writing a legal document, don't do it quickly. Write it, come back to it again to review. Is it still a good idea?
If you are doing something completely new, do it slowly and step by step -- if it is new you don't know if it is right without checking each step.
If you have an idea, read the literature, patents, see what is out there first.
But, if you are writing an email to a person whose time is valuable, better not to do it quickly. Save a draft, come back to it tomorrow, read again, then send.
If you are writing a legal document, don't do it quickly. Write it, come back to it again to review. Is it still a good idea?
If you are doing something completely new, do it slowly and step by step -- if it is new you don't know if it is right without checking each step.
If you have an idea, read the literature, patents, see what is out there first.