Whether it is true or not that in markets like Bitcoin (crypto) ; one person gains only when the other losses some thing. Suppose one person bought one Bitcoin for $5000 in January 2017 and sells in June 2017 for suppose $10000 he gains $5000 by selling. Now the purchaser in June 2017 @ $10000 sells it for $6000 in January 2018 and as a result he losses $4000. So it is clear from the example that the profit of seller in June which was $5000 includes the loss suffered by the person who bought it in June 2017 and sold in January 2018.
If there are some other reasons for this profit / loss factor, I request other members to please share their knowledge with the platform because my opinion may be on the basis of partial truth and there may be other factors responsible too.
That is the greater fool theory. That is the case when people are trading without knowing the intrinsic value of something.
If the ability to own an innovation that allows you to make financial transactions free from third-party control and disturbances is not worthwhile to you, you should probably not invest in bitcoin.
If you think that bitcoin has the ability to make our society more open, our banks more compliant and wealth distribution better, then you are welcome to inform yourself about it and invest what you can afford to lose.
Bitcoin is the only crytpocurrency with this level of underlying infrastructure, tested under extreme conditions already and a huge community of adopters and developers. None of the others have even approached the scale of usage. Bitcoin has been there, done that.
As crytpo gains momentum, bitcoin will lead the charge. That is its intrinsic value and you should try to increase your holdings without risking your economic well-being.
We are at the cusp of great changes and its your responsibility to inform yourself and make an educated decision. In the greater fool theory, its the foolish who lose.