Holding coins really depends on when was the time you bought it. As of today most coins drops for the average of 50-60 percent based on thier highest price. Like for example bitcoins highest price of all time was almost 20,000 usd, right now the current price is around 8,500-9,000 usd. So if you invested at the time when bitcoin was around 18,000-20,000 then you really are messed up, but if you buy today, it is possible that it could return to its highest price or even higher. Just study the market, study the background of the coins you wish to buy, read currrent news about cryptocurrency and always monitor the movement of the price of your coins. Considering all of this, and you can now decide when to sell or to hold you current coins.