Therefore, I believe delaying investing in Bitcoin until we have discretionary funds is a bad idea. Time is ticking and can't be undone.
Don't you think you are getting it wrong here? That we should invest in bitcoin even when we have not figured out if we have a discretionary income to invest so i believe it's still ok to wait if there is no discretionary income to get started with.
The reason you should invest with your discretionary income is that things might not go as have plan it might go dip so if you invest with discretionary and such thing happens to occur you won't get your self up set because you invested with what you are afford to loss .
I do not agree with the stance that one should invest quickly, as time is ticking. If anyone has such a mindset, then he will surely incur losses, or even if he does not sell at a loss, his portfolio will be in unrealized losses. One should invest after due diligence and also in parts. People usually invest all in bitcoin (or any other altcoins) at once, thinking that it will only go up from here.
Investors need to understand the market but unfortunately, most people come into cryptocurrencies thinking that they will become rich overnight. That's the reason most people lose money in crypto, and very few are able to make a profit from it.