As long as you don't sell while the value is down, you do not lose any money. HODL until the price recovers.
Too many people panic sell.
This statement is only true if the market is guaranteed to always go up in price.
Why do you believe that this market will ALWAYS go up?
Spoiler alert; I think that Bitcoin will recover and go higher in the future, but I also think that it has further to drop and will reach lower lows in the near term. Around $2500 for Bitcoin and $100 for Ethereum.