Leaving aside the monthly money that needs to be spent on living, buying Bitcoin with every spare dollar you can find is the thing to do, no matter the BTC/USD price. It will pay off in the long run.
If you think 2 days later you will need that money, don't put it aside for investment in the first place. Investing is not a short-term business.
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the best practice buying with every spare dollar, since you are still supposed to build variances of your backup funds from those spare dollars, otherwise commonly referred to as discretionary income. You have a great investment practice by investing a percentage of your discretionary income into bitcoin, although I would recommend, but not limited to 50% to 70% of your discretionary income into bitcoin and keep the rest for building out your emergency fund and other variances of backup funds and keeping floating cash as well.
When you invest all your discretionary income into bitcoin as a new investor, it can as well be described as being over aggressive in your accumulation and this can be detrimental to your accumulation journey in the long run, coupled with the fact that you may not be able to sustain it, and your investment is at the risk of being tampered in case of any emergencies since you have failed to build out your emergency fund alongside your buying bitcoin