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Surely you can use your discretionary income for any type of investment you want to venture into, and nobody will stop you from doing that because it is your discretionary income. You can even choose to give out your discretionary income to members of your family since it would not stop you from sorting out your daily expenses. Since you are investing you discretionary income into bitcoin, don't see it as money you can't afford to lose because it is your leftover money, and you can even decide to go on vacation with it if it is good enough to handle a vacation trip.
Hahahahaha.. maybe examples could be fun, too?
Maybe one week we realize that we have an extra $300 in our weekly pay, and we are trying to decide what we are going to do with our extra $300... maybe we will buy BTC? Maybe not.. let me think about it?
Then maybe I am walking on the beach, and I see a party, and I see a Ice cream cone vender, and I see that the Ice cream vender sells his ice cream cones for $6 each. I asked him if he would give me a discount if I ordered 60 ice cream cones. He told me that he would charge me $5 for each cone if they fit certain criteria.. .. so then I agreed and I order 60 icecream cones to give to attendants at the party that was going on nearby. I used that money to buy the cones and not to buy the BTC.
Another option could be that I was in the mood for hookers and blow.. so I knew about a place that I could pay $100 for a hooker, and I could buy blow for $100, and I also figured out that I could rent a Lambo for 1 hour for $100. So I decided to spend my $300 on all three instead of buying bitcoin with it.
Surely both of those categories of spending the $300 in the above examples relates to what I could afford to lose, but instead of buying bitcoin with the money, I decided to consume all of that $300 with icecream cones in the first example and with hooker, lambo and blow in the second example.
I could afford to consume or I could afford to put it into bitcoin for 4-10 years or longer.. either way, I categorized the $300 for that particular week as an amount of money that I could afford to lose.
Sir JJG I love this example it made everything more clear to me and I now understand that truly discretionary income and money you can afford to lose is really the same, I was thinking that "money you can afford to lose" is the smallest or the lift over money in discretionary income, for example I have a $100 discretionary income for the week or month and I use $80 or $90 for fun and other things I wanted to do and if $10 to $20 is lift over before receiving another salary that's my " money I can afford to lose" but from your explanation it simply means that the remaining $10 to $20 is still part of my discretionary income which is same thing with " money I can afford to lose" I get it clear now.