I have gotten some nice knowledge concerning bitcoin investment in this thread and am still learning in the process 700 pages of bitcoin knowledge and still counting all thanks to JJG and other reputable fellow in this thread.
If you are a HODLer keep buying and hodling bitcoin if you are still procastinating on when to buy you can buy today if you have your discretionary income already starting buying and HODL you can begin with little amount and gradually increase according to the level of your discretionary using the DCA strategy.
Just buy bitcoin and HODL in summary.
Having what it takes to buy and hold is a different thing from not having what it takes to invest in Bitcoin, there are individual who has the money and all takes to invest in Bitcoin but they keep on procrastinating and these category of people I see them as unserious people because anyone who has all these... And is still procrastinating even if the person eventually start, they can not maintain their investment or hold for long because their knowledge or understand about Bitcoin is so myopic. In Bitcoin investment though having a discretionary income is good but it is not compulsory that you must have a discretionary income before you can be able to invest, you can actually start and make sure to set everything in order so that you don't get choked up and the truth is you can not have everything ready before investing but along the line things well fall into their right places and you can even increase your initial amount.
It is with your discretionary income that you will use in accumulating Bitcoin so having a discretionary income is compulsory you discretionary income is your leftover fund this is money set aside after you might have settled your pressing needs this will make you not to sell your bitcoin unmatured when personal needs may arise so having discretionary income in important and compulsory.
You have a point about having a discretionary income helping Bitcoiners to hold their bag for the long-term due to a lot of cases of people selling their BTC unmaturely because of emergency needs. This reminds me of a Reddit user who posted about selling some portion of its BTC to solve a health issue after accumulating 1.003BTC.
Having said that, another important thing when accumulating BTC is knowing to securely hold the coin because if a Bitcoiner have the needed discretionary income but still lack the knowledge to secure the BTC s/he is just like people who don't hold BTC at all.