Let me repeat: rating is important (see my last blog), but rating is not everything.
If you replace rating with money, grade, career success, and etc., you will see similar cliché.
Rating should motivate you work hard, not paralyze you from taking actions. You should never think about rating during your games. Not your past rating, not your future rating, or not even your opponent's rating. You only think about it during your long term planning. Fearing possible rating drop is one reason people take easy draws.
http://www.completechesscourse.com/puzzles.html
http://onemovecheckmate.blogspot.com/