I think all the small investors who have the habit of selling Bitcoin actually don't understand anything about investing. But I don't agree that big investors have a habit of selling Bitcoin, in fact they are called big investors because they buy Bitcoin regularly and own a lot of Bitcoin. That is, they are very experienced and patient, so they have been able to increase their Bitcoin holding, and even have a lot of patience to maintain their investment. So it would be wrong to say that big investors have the habit of selling Bitcoin.
Not only is prudent income necessary for small investors, it is much more important and necessary for all investors. In fact, in many cases, many use the words prudence and disposable income, so they should know properly.
Everybody needs to fix their profits eventually.
The thing is most smaller investors are not standing on the same stable ground as the bigger ones - they still need to think about their potential risks and much more, whereas guys in suits and a bit lower don't need to think about it.
Is not that small invests that have habit of selling their Bitcoin does not understand investment, most of them understand investment but the truth is that some of them don't have the financial capacity to solve some of their basic needs so when they have any financial pressure on them they tend to sell up their Bitcoin to enable them raise money to solve their financial problem. This is the reason why it's important for every Bitcoin Investors to have alternate source of income or a descrisionery income to enable them be able to solve their financial needs without affecting their Bitcoin investment for long term holding.
Anyone who sells his or her investment when it is small, it is either the person is a gambler or the person don't understand Bitcoin investment because if you are not a gambler you should understand that the best and advisable way to go about Bitcoin investment is to use what you can afford to let go that is something you won't feel even if something goes wrong and someone who understands Bitcoin investment should always have a discretionary and a reserve funds, using your discretionary to settle challenge is still not good rather what you should use to settle challenge(s) is your reserve funds so don't get it twisted.
Do not classify all investors who sell their bitcoin when it is small as gamblers. Some investors can sell their bitcoin too early when they use all their money and invest in bitcoin, and when their daily expenses arise, they will have no other money left that will help them take care of their daily expenses, so they will have no other choice but to sell their bitcoin during their accumulation stage to get their daily expenses sorted out. Just like you said in your post, anyone who wants to get it right with bitcoin investment should always use his or her spare money or the money he or she will not be needing for a very long time so that he or she will always have 100% control over his bitcoin investment.
That is why it is necessary to have a separate emergency fund when investing in Bitcoin, this emergency fund will help to deal with any danger. My opinion is that a person will not invest his entire income in Bitcoin, if he invests the remaining money in Bitcoin monthly or weekly, excluding the basic expenses of the family, with that which he spends more, then he will be able to invest in the most appropriate way.
You are learning these methods because you should abandon the bad habits you had and add those funds to the Bitcoin holding, then you will see that your Bitcoin holding will reach its highest level within a few days. However, it has to be implemented according to the plan, that is why an emergency fund is most needed for an investor.
Maybe we should stop having that tag or spare money rather than money we don't have immediate or close time usage for to invest on gambling because sometimes we think about just playing around with an unbudgeted funds on bitcoin and later on unnecessary or necessary need to make use of the fund arises and will be pushed to sell. Why? Because we haven't been mindedly ready to invest in bitcoin then but if we've to have plans for bitcoin investment, we can always have portions of our incomes set aside for it or even money ought to be saved in the bank for long time or probably for retirement as usually lot of us or our people has been doing before this digital investment era can turn on to saving on bitcoin.
Then with the plans of the long time investment, we can be left not to sell on immediate pressure needs.