Its normal especially to newbies in bitcoin and trading to panic when the price is going down. They tend to do that because they lack experience and enough knowledge about the nature of bitcoins and trading. But the longer they are in the business and their experience becomes wider then they will no longer panic and just do proper trading leaving strong emotion aside that impedes their judgment.
Well if you see most of the people who have invested are newbies itself. There are very less people who actually take the effort to
know more about the currency and how it works. Basically people see that bitcoin was 0.1$ some 7 years ago and now it is 900$ so
they invest in it. And when it reaches 1000$ and starts falling a bit they start selling.
If they only look at how the price has performed in last years, and take for granted that it will happen again, then they are just blindly buying (also known as gambling) themselves into Bitcoin. If you take into consideration that the price tanks heavily every now and then, then it's just a matter of time before these people get shaken out of the market with heavy losses as result. They either learn from it, or simply remove themselves entirely from investing in Bitcoin.
What makes you say that bitcoin is gonna disappoint it's investors. I agree there are ups and lows but if you see in long run it is profitable. The limited supply is one of the reason that makes me trust on the currency that it won't end up like gold. Even though most of the investor do blindly invest but I don't think they will ever regret about this in the future.