Do you mind being specific, as you have said, you made good profit at the beginning, does it crash the altcoin you have bought or you have made a mistake of not taking a profit? If it does, then it is a personal judgement that becomes the reason for your losses.
I don't say that I do not trust bitcoin, but what you have said can also happen to Bitcoin. It can crash in a blink of an eye, many have experience that, the price suddenly drop at an unexpected price, though Bitcoin will surely be able to recover and the its price still grow over time. Bitcoin is indeed strong compared to altcoins, we just have to put our trust on it.
Yes, this is it. Some of the Altcoins that I invested in collapsed after witnessing significant growth, and some of them I made the mistake of not taking profits when they reached the top because I expected them to rise more than that.
Other times, I made big profits from the rise of the coin, but after its price fell, I bought large quantities in the hope that it would rise again, but it continued to fall and I had to exit with a loss in the end.
Of course, you can say that this is because of my personal mistake and that Bitcoin is the same thing, but at least if the price of Bitcoin falls significantly, you can hold in the long run and you will emerge profitable in the end.