That's a common mistake among new investors. They don't have proper investment plans, they invest every money they have in Bitcoin hoping to get quick profits whereas Bitcoin investments are usually good for the long term because the price in the short-term is more unpredictable.
That is why it is said to invest only as much as you can afford to lose. Moreover Bitcoin investment is not that you will be able to earn profit from it just by investing and Bitcoin is not a get rich quick scheme. Bitcoin investment is likely to be successful in long term but short term investment can be profitable if you buy large amount of bitcoins at once during dip season and sell it during bull season.
That is the reason why the DCA strategy has made it very easy for anyone both those that has large amount of money and those that doesn't have to come in terms with Bitcoin and as well become a beneficiary of the true potentials it holds by investing only the amount you can be comfortable with either weekly or monthly irrespective of the price points and hold for as long as possibly 4 to 10 years or more. There is no such word like short term investment in Bitcoin but rather it should be referred to as trading for a short term profit maximization over short frame of time. It is gambling than investing when you buy Bitcoin at the dip with the intention of selling when in bull, because you can buy now and the the market might dip further.