Yes, in order to invest in Bitcoin one should not invest more money than one can afford to lose. Now if you invest more money than you can afford to lose then it will be risky for you to hold the investment for long. If you invest with what you can afford to lose then you don't need to sell bitcoins for urgent needs. Besides, money should be saved for emergency use. Now I never invest more money than I can afford to lose.
Investing with an amount you can afford to lose? No.
Who would want to be investing in something he is not certain off?
Or are you trying to say that it's very much important to invest an amount of money you can do away without for a very long period of time?
Know the difference between these two statement bro.
Though we live in a world full of uncertainty, but no body would want to invest his or her money in something that is 50/50. Bitcoin investment is not gambling bro, but in my own opinion the ideal word you should be saying is invest only what you can do away with in a very long period of time, so that you wouldn't fall back to your investment when in serious financial needs.
The word what you can afford to lose is what I think you misunderstood because that word doesn't necessarily mean you are investing to lose your money, do not get it twisted, there is no guarantee that every Bitcoin investor is going make profit unless the investor understands what Bitcoin investment is all about and is able to take advantage of the market to buy during the dip so they can take profit during the bull.
The mindset of every investor is to make profit but being honest I think there is no certainty that every investor will make profit as some have even gone broke as a result of wrong investment plans, Bitcoin investment doesn't guarantee 100 percent profit but it doesn't mean the investor will lose everything if he understands what he's doing.