Your account value is based on how much Steem, Steem Dollars and Steem Power you own and simply converted in US$ at the current rate. When the price of STEEM falls, your account value falls too, when the price of STEEM goes up, your account value goes up too. So, basically, you're not loosing steem, simply steem is losing value against the US$.
RE: Save money from your Steemit wallet