Although you are right, we have to remember that the formula is the same in trading and investing. That is, invest and trade with the amount of money you can afford to lose. Only when you are able to lose the amount of money will your energy and inclination towards investment work, but you will not be emotional. Many times it is seen that people are afraid of investing, but instead of being afraid of investing, they participate in the investment with the money that they can afford to lose.
What you really mean is that both investing and trading involve risk. Those who are going to invest or trade should invest with risk because sometimes you can make money from investment and other time you can lose your money from investment. So invest as much as you can afford to lose.
Firstly investing and trading are two different things meanwhile if comparing the risk involved I will consider trading as a risky move but, this topic is not about trade and if anyone should trade they should be knowledgeable first but still doesn’t give full assurance. Investing is more safe because an investor will hold for long term with what’s available, this statement is kinda complicated “ invest as much as you can afford to lose” the lose you mentioned simply means some day everyone might just not see any profit as anything attach with lose makes no progress. Bitcoin investment has no lose except the investor doesn’t want to hold for long that’s when we can say an investor is taking a risky move but, if we’re holding for long term we should not expect lose but rather profit in return. All what an investor needs is just the right strategy that suits their investment and plan to hold for long.