As a dentist, I see many problems with dental hygiene and most of them stem from improper brushing and flossing. I found this infographic made by Cynthia Eubanks that helps illustrate many of the failings almost all of us have while brushing at some point or another.
It’s true that over brushing can weaken your teeth, especially if you are using a rough or hard bristle brush. I always recommend a soft bristle brush, because they gently massage your gums and teeth. And it may be seem surprising, but it’s actually better to floss before you brush, rather than after!