Let me explain this better. I will do this using apples.
You spend your entire life collecting apples for your retirement, and you've collected 100 apples. This is called your "apple net worth". But the recession comes and you loose 60% of your apples, and now your apple net worth is "40 apples".
As the economy gets better you start collecting more apples again. After a few years you've collected another ten apples, bringing your apple net worth to 50 apples.
You still have less than 100 apples, which makes your apple net worth look smaller. However, the truth is you have ten more apples than the forty you had a few years ago, thus your apple net worth is up.