I agree with your words. However, along with discretionary income, basic knowledge, and proper investment methods, another important thing that should be there is patience. Many people have a lot of money. They have invested in Bitcoin in the past. But when the Bitcoin market went bad. The price decreased compared to before, they lost patience and sold Bitcoin. But later, when the price of that Bitcoin became much higher than before, they lost that opportunity. If they had been patient and confident and had invested for a long time or had held it, they would have made a comparatively much higher profit.
Basically, weak investors face such a situation, when there is a slight dip in the market, the weak hands get scared and decide to sell their Bitcoin investment. But in this case, I want to say that if you invest in Bitcoin strictly following the DCA method for the next few years, you will definitely be able to sustain your Bitcoin investment for a long time. And some more steps are needed. If you want to sustain your Bitcoin investment for a long time, you definitely need an emergency fund.
Because the emergency fund will play the biggest role in saving your Bitcoin, if you face a small danger, you will definitely be rescued by this emergency fund.