that is the story of a great number of "traders" in this market, and most of them never learn their lessons. I somewhat agree with the first reply but I say he might have learned his lesson only if he doesn't come back ever or only comes back when the educates himself. but in my experience these types of people never change. soon enough when the big rises begin they come back and again lose money because of bad decisions. in some cases it is even like an addiction!

and that doesn't stop there either, some even go to altcoins since they lost money in bitcoin and then get crushed even harder because they suddenly decide they should bag hold altcoins and as they get dumped on them (since they are pump and dumps anyways) they lost all their money there.

I also experienced an mistake in trading, at that time I invested in Ethereum. March 2017 I bought it when the price was 19USD. When in December ETH prices reached 800USD and I still held them because I thought the value would continue to increase. entering 2018, I sold it with great regret.

I do not have any problems with my relatives, because I explain the risks involved with an investment into Crypto currencies in advance. They MUST know what the risks are, BEFORE they invest and they must understand that this technology is a HIGH risk investment, because it is still experimental. 

They should also NEVER use debt to fund their investment in Crypto currencies, because nothing is guaranteed in this scene.  Then it is all on their shoulders to make the decisions. Tip : Let them start with small amounts first. 

Well wrote OP. And this is the true. I have few online friends once bitcoin was $3.1K I have suggested to buy Bitcoin, but they refuse as well. But when bitcoin has been touched $4.5K then they were asked me to buy. Then I said during my suggestion you had not buy then why are you asking me? I don't know after that they bought or not. Usually people's behaviour is greedy. So during pump they like to buy and eventually they get REKT. Lot of people's wonder to buy during pump. But during dump they think it will go more down so wait wait. But really we don't know where is the bottom. So if you found bitcoin yearly bottom then we should take entry.

You called him a stupid trader, but he is not a trader. He is just an investor loser. There are many of those. People invest money in something they don’t understand at all. And your friend did the same. At first he did not want to invest in Bitcoin, because he did not see his prospects and then decided to drop into the departing train. Greed won out over common sense and he bought bitcoins for $ 15,000, and then became disillusioned with cryptocurrencies because he lost money instead of making quick money. There are 80 percent of such people on the cryptocurrency market. And they will always be. With this you just have to accept.

That's a perfect example of human psychology. People were FOMOing into BTC when it was at or near its all-time high, but when it collapsed they sold and lost interest. They will then jump back in when BTC hits new all-time highs. One way to come to terms with this is by recognizing that this tendency of human psychology presents solid traders and investors with a golden opportunity.

I like this reply. Your right - He wasn't a trader - just an investor loser 

Which, I hate seeing. I want people to make money and to be happy with crypto, and being a relative it kind of hurt me to see him lose so much.

I guess it also kind of hurt that he just went out and bought a significant $$$ amount without even considering what I would say - Which is why I call him a Stupid Trader.

As with other comments here - I fear that he will do it again in the future if/when Bitcoin starts pumping again. Like someone had said, at $100k he will most likely re-buy and get burned a 2nd time.

What makes him not believe in your words? I read your story, it's really very sad if your sister buys bitcoin when the price is high. If he follows your words, he will benefit several times.

The truth is no one really knows for certain what the future holds.  Most of us on this forum are bullish and expect bitcoin to last for a very long time but its still young and a lot of the skeptics have good points.

Investing and trading isn't all about intelligence but rather about keeping your emotions in check.