Surely if someone is investing 100% of his discretionary income into bitcoin that might be on the border of too aggressive because he might not be adequately accounting either his income or expenses, so there would be no room for mistakes, unless, he were to invest that amount at the end of the pay period rather than at the beginning, meaning that if he were to only make his investment of all his extra money right before his next check had arrived, so then he would be at least eliminating the possibility for mistakes, so then his next period starts again after his check for the next pay period arrived.
There could be some folks who say that they are doing 100% but they really are not because they are keeping various kinds of cash cushions, but then they could still be accurate in claiming that once they calculate their various kinds of cash cushions are in place, then they will invest 100% of their remaining cash into bitcoin, whether that is weekly or some other period of time of spreading out the buys.
You are very right here! Investing 100% of discretionary income into Bitcoin is generally not advisable. This is because the investor is jeopardizing everything he earns thereby putting them on high risk since Bitcoin is a highly volatile asset. Another reason is because one should not put all his eggs in one basket, diversification, emergency fund, business and small savings is really important for an investor so that they wont get to tap into their investment. If a person invest all his discretionary income into Bitcoin he leaves no room for a safety net.
No matter the price action I feel that there will be more work opportunities in the future. It is good to use for something meaningful just like investing but not all of them into one thing. IMHO People should stop (especially beginners) converting their discretionary income into Bitcoin until they have achieved the necessary mental balance they need of multiples business, emergency funds and month budget expenses. These application does not imply to the rich because they have more than enough to invest and enough to remain.