@Ginny,
Many of us have been perplexed by this. We proof read our posts or emails, and then once we send them along we discover errors that were obvious.
My theory for this is that when we are sending a message, we are accessing different intuitions and patterns in our brains then when we are simply receiving a message. When we are proof reading our own writing we are still in writing mode; it's not until we see our words in the context of the audience, that our brain switches over to the specific patterns we use for reading.
The next time you are typing an email, try sending it to yourself first. It's surprising how "different" our words feels when they appear to have come from someone else. The feeling is much like seeing a strange person in a glass window for a second, only to suddenly realize that the person you see is yourself reflected in the glass! For that brief moment you had an opportunity to see yourself void of your internal intentions.
Another example of tricking the brain into pattern switching is the way an artists will use a mirror to get a fresh look at their work in progress. Looking at a portrait in a mirror suddenly reveals any flaws in symmetry or other jarring defects that were simply not "visible" to the artist's own eye.
Proof reading is learning how to see our own writings as they will be read, not as we intend them to be read. We sometimes need help in seeing past our best intentions!
MC
