Bitcoin investment is risky just like any other investment but the risk is lesser and if you invested with a discretionary income, there is no need to think about the risk that is associated to it again since you can bear any aftermath of what comes out from your investment if things peradventure goes wrong
You thought wrongfully about it.
Invest what you can afford to lose is a very classic advice and by invest your discretionary income, you do your capital management better. Risk is risk and it is nearly the same for your investment capital, and if you picked a wrong cryptocurrency for investment, you will have same 80% loss of your initial investment capital. It's not matter that your initial capital is $100 or $1,000, it gives you same -80% ROI, that is insane and painful.
@Btcdeybodi is more correct on this context than you because his intentions of discretionary income speaks why is only important to be use on our bitcoin investment, don't think that financial management is not associated with discretionary income because before having discretionary income there was other money attached to it and since there are other necessary things it got managed to served all the purposes and when there are no more things, the little that's left is now use to invest in Bitcoin, so actually there was a serious capital management on discretionary income and is the most appropriate way of Bitcoin accumulation.