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But I think I was more lucky to sell my coins at 2017 for huge profits but the real problem is I can't save much money to get those stash back.Hopefully I can save money.
Yeah, but many of us are familiar with a dollar cost averaging concept.
Of course, I don't really know much about your personal circumstances, but I always suggest for BTC investors to largely get their finances in order before investing in BTC - however, sometimes, it would take too long to get everything in order, so you have to prioritize various aspects in order that you don't have some kind of an emergency situation that causes you to have to cash out your BTC at a time that is not of your choosing.
In that regard, sometimes, even when cashflow situations are tight, you can buy in very low price amounts, such as $5 here and there or $50 or just spare cash... I have a system in which I project my cash flow for 6-18 months, and make sure that I always have at least $900 in my banking account (as a cushion) (and of course I have other funds that I could draw from too, if I were to have a 6 month long emergency or something like that), so if I have new cashflow come in or new expenses, I can plug those amounts into my cashflow projection, and if my amount of cushion in my cashflow projection goes over a certain amount, let's say $1,000, then I can take up to $100 and buy bitcoins with that.... and I still maintain my minimum required cushion of $900.
Also, maybe if I was running tight on my cashflow, and suddenly I found myself with $100 extra to buy bitcoin, I might put that $100 in a Bitcoin buying fund, and then perhaps buy $25 per week of bitcoin with that for the next 4 weeks, or something like that.