You don't lose money in Bitcoin unless you sold.
True and not true. Loss or profit is on the screen or paper in your calculation and it only becomes actual profit or loss if you sell your bitcoin to have cash.
The vital point is if a person used all money to invest in Bitcoin, no other source of money for emergency, he will have to sell his bitcoins when he takes profit proactively or has to sell it for emergency.
Bear market is inevitable in any of the market, if your focus is a long term holding and you were caught between the devils market crash, you continue to hold and buy more as the market continue to dip, buying that way is what is term as dollar cost average(DCA), you will reach a break even points where you wouldn't have profits and loss, you can chose to withdraw your investment in case you change your mind or you may hold as you intended from the beginning.
Before thinking of a bear market, buying more in dips, you must think of your financial status in a bear market and what you already prepare for it.
As said above, if you don't have any money reserve, you can not buy any dip but it will come to a time you have to sell your bitcoin even you only want to hold it. Because without cash to use, how will you live through a long lasting bear market?