money to buy BTC.
You can invest your entire discretionary income if you want. But it would be better for an investor to invest 25% of his discretionary income. If a person uses 25% of his discretionary income, then he can build an emergency fund with the remaining 75% and if the emergency fund is ready, then he can keep that money with him and when he sees a decline in the market, he can buy aggressively.
I think that with time an investor does everything. Maybe a new person may not do this, he may not be aware of this. But a person who has been investing for some time may set aside money to buy aggressively. Because he knows how to use the decline.
Older investors often don't take advantage of price drops if they want to buy Bitcoin more aggressively, although they don't dismiss them as a good opportunity for those who haven't been afraid to buy without the market dropping. And such investors are usually not afraid to use half of their income to buy Bitcoin because they can still manage their lives with the remaining half. Therefore, this will never be the same for one person as the mentality and courage to buy assets like Bitcoin always differ from person to person.
Furthermore, there are differences in income levels among individuals, and this can influence how they use their money to buy Bitcoin more aggressively on a regular basis and less focused on price declines in the market. So, I'm not at all surprised to see investors who invest half their income in Bitcoin every week. Even though they are still concerned about their own livelihood and emergencies, their courage in regularly investing half their income every week is truly admirable.