I happen to think the odds are far greater in favor of BTC going to $5000 than it going to $5 actually. So I partially disagree.
I do agree though that you should not invest more than you can afford to lose, but that goes for pretty much any investment.
I think the bitcoin will go to $5000 some day in the future, but it could be 3 to 5 years. $5 is not possible.