I agree with this statement. The simple retention of the crypto currency does not always bring a good profit. Often, coins and tokens through some even a long time again come back to the price at which their retention began. Therefore, in addition to carefully selecting the necessary coins or tokens for retention, it is also necessary to trade them, selling at least half of them when they are high enough to rise in price and then buy when such a coin or token falls in its value. With this approach, you will always have a good extra income.