There is a golden rule to live by: never invest what you cannot afford to lose.
FOLLOW IT.
This ^^ a million times over!
It's generally a good rule, though sometimes the people who take the risk and go YOLO are the ones who win big, but of course the opposite is also true. I'm a big believer in bitcoin, but I'm not a big believer in people and those are what we need for bitcoin to push through and become very succesful, so I only invest a little of my own money and try earn bitcoins in other ways as I know it's not a foolproof investment. Saying that though, you could invest all your money in bitcoins now and sell as soon as they double or something, which I think is likely to happen, but it's not guaranteed and of course is a risk. Whether you take that risk is down to you to make.
Going "YOLO" is a very good way to end up broke and is essentially playing the lottery. As long as you will not need the money you are risking in a long time and have the ability to save to make up potential losses then it is acceptable to risk money that you will need in the future. This is essentially how people should save for retirement.
The best investors will make calculated risks that have a good risk to reward ratio