Exactly, Mr. JayJuanGee what you said is absolutely right, it is advisable for someone to use discretionary income if he wants to invest into bitcoin, gambling or buying shitcoins. You can not invest your total funds in bitcoin investment or trading, bitcoin investment is very risky and so also trading, just because you started your investment with a huge amount of money doesn't mean that "the higher the capital the higher the return", you may loss your fund with blink of an eye, the possibility of earning profit that you have at the back of your mind, put at the back of it that there is also a possibility of loosing your money too, that is why it is often said that you should trade with what you can a to lose. Don't be so eager/impatient to make huge profits because it may land you in regret.
Actually in this case I have some things that I agree with and some things that I don't.
I have the same opinion when saying that in gambling, investment or anything of course everything refers and uses discretionary income but on the other hand actually I don't really agree with your last sentence that you should trade with what you can afford to lose.
I'm a bit ambiguous here because I think no matter how much money we have at the end of the day when it comes to trading then you have to be prepared for the worst and regret it at the end. Not that I underestimate those who trade but at the end of the day bad luck always happens and we have seen so many people liquidated just because of failed trades so in this case I would rather say that when you trade then you are bound to lose not prepare to lose.