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I think you failed to understand that your discretionary income comes from your salary or from the money you make from your business. And I found this your comment above confusing, because I don't see any reason why you said that our discretionary income should be use to accumulate bitcoin, while our salary and money coming from our business should be used for settling our basic needs and expenses, and you forgot that our discretionary income from those two source. Instead say that will should only accumulate bitcoin with our discretionary income and not with money meant for settling our basic needs and expenses.
From his statement you could understand that he has an idea but still got some little misunderstanding concerning how the discretionary fund is generated, atleast he knows that investing on Bitcoin should be done with the discretionary fund which is very important, it's good you brought to his notice that the discretionary can be generated from his salary or a business so when next he's discussing about the discretionary he'll know the appropriate things to say, we learn everyday and I believe he's learnt about that and taken the necessary corrections which is what this thread and the forum in general is all about for those who are here to learn and add to their knowledge about Bitcoin.