Your discretionary income is that extra money that you don't have plans for after you must have taken care you your basic needs and monthly expenses. Some people use their extra money to gamble, club, drink, womanize and many more but it's wise for you not to use this funds for consumption purpose. Rather, invest it into bitcoin and save the value of your funds for the future.

Investing with your discretionary income allows you to pile up more bitcoin for yourself overtime and hodli till your desired time.