You mean, you've cashed it in?
You only "lose" when you sell. Your contributions now are buying more shares for later.
Back in the dot com implosion and subsequent recession in the first quarter of 2001, my retirement plan value went from about $ 310,000 to $ 165,000 without me selling a single share of the balanced funds in which I had invested. I still had the same number of shares, the value per share dropped significantly. It took me five years for my plan value to recover to that level by continuing my usual monthly contribution, employer matching and reinvestment of dividends. 10% of my pre-tax income and 3% employer matching goes into my account every year. So, yes, I consider drops in value as a loss, since if I cashed in my plan at that particular time, there is somewhat of a difference between $ 310,000 and $ 165,000.
It all goes to timing of when you cash in or start to draw from your plan. If the market is tanking at the time, those aren't just paper losses. They are very real.