Old rule. Repeated many times but the mistake will always happen. Investors tend to make an error using loans just to invest in a bear market which for me is another addition to the risk factor of investing in cryptocurrencies.
It's not just what you can afford to lose, it must be your own money that you are risking either a part of your savings or just your leftovers for being thrifty. Also depends on the right timing of purchase, there will be times when a bear market looks like it reach the deepest but it may not, like what happened with Bitcoin.
Actually, it's okay to make mistakes when investing, because from these mistakes we can learn how to invest properly. The most important thing is
that we don't repeat the same mistakes over and over again. As you said, investing using borrowed money, that's a mistake that many investors make,
they think crypto can always make a profit. Whereas when investing in crypto is not necessarily profitable, while borrowing money puts us in debt,
the problem is that debt installments must be paid regularly. Therefore, it is highly recommended to avoid investing using borrowed money.
Another mistake might be choosing the wrong coins for investment, even though the market is declining, does not mean that all coins can provide profit
if purchased at a low price. Because some coins when we buy the price goes down and we will find it difficult to sell them again. So make sure
we do research and analysis before buying coins, so that we don't choose the wrong coins for investment.