You didn't "lose" your balance. You didn't go from having 1000 shares to having 800 shares. The shares contracted in value, and will likely come back over time. Plus, those were speculative values to begin with, not real value.There is no good spin that can be put on losing 21% of your account balance.
In 10 years it should bounce back. A big chunk of the value in your 401k is what you contributed during the down years of 2000-10 because those shares had far more room to grow.I'm 2 years away from the age when my father retired very well. I'd love to retire in 10 years but that is looking less likely all the time.