Your statement is limit supporting what is wrong under the disguise of freedom. In Bitcoin investment, you don't do the wrong thing and say that everyone have the liberty to do as they please because you will just run into problems. The essence of threads like this is to teach people the right thing so they can do better and be happy in the future.
The right thing is to buy Bitcoin with only discretionary income so that they will not be under pressure to cash out all their Bitcoin at any time. If they sell all their Bitcoin, they will run out of Bitcoin thereby defeating long term hold which is the recommended way of going about Bitcoin. If you have no discretionary income, then it is time to find a job or look for way of improving your finances before thinking about investing in Bitcoin.
Not all Bitcoins should be sold up on the way up, because, yeah, clearly, more would be lost than achieved doing things like that: however, making mistakes, although they can be avoided, is the best way to learn and remember what was done wrongly.
And, sure, a stable job and income mean a stable investment process.
You don't necessarily need to sell anything from your holdings if you are still in your accumulation stage because by thinking that you can outsmart the market is unwise, because by selling some of your holdings for minimal gains, thinking to buy back when it dip you are practically selling off most of your future revenue for peanut today which will make no much difference on your finances now, and you may never buy at that dip you thought you might get, so it's a move that should be avoided by all means.
Take note that am not against selling or taking profit from your Bitcoin holdings, but let it never be done when you are still in your accumulation stage.
If you are not in profit especially if they are starting up then its bad decision to sell since they are losing if they are doing that and months of efforts will be wasted, then provably they would regret doing this decision especially if the market moves up.
This is why its important to have emergency funds so that if there's emergency situation they can use this funds and they won't think about selling their Bitcoins.
Although there's nothing wrong to sell especially if they think about selling a little percentage of their profit because they really have important thing to spend their money with. But if there's no like this exist and they are just thinking about selling better not to do it and much good for them to focus their attention on buying more Bitcoins since there are chance that they could earn more from it in future.