I think you don’t have to wait till you get all the mental preparations or anything before getting started in bitcoin investment.
To start investing, you need to be mentally prepared so that you can start investing freely and have confidence in the investment. If you have not yet been able to establish enough confidence in the investment due to lack of knowledge or your mental state is not suitable for investment, then I think it is not wrong for you to delay the investment for a while. For example, if there is a disruption in your normal life due to some issue, if any incident around you disturbs you mentally or if there is a shadow of grief in your family or your personal life. In these situations, I think your mental state is not at all conducive to investment. Or you must be mentally prepared before making any long-term risky decision. This requires some time and good advice. However, it is not at all appropriate to delay the investment by making excuses, I do not see anything wrong in delaying it for any reason.
Therefore, I believe delaying investing in Bitcoin until we have discretionary funds is a bad idea. Time is ticking and can't be undone. Rather than training our mentality first, it's better to just start investing. I emphasize again that this mentality will naturally develop once we start investing, and a naturally formed mentality is better. Because, the real test lies in real-world situations.
If we want to accumulate Bitcoin, we don't use mentality to accumulate Bitcoin; what we use to accumulate Bitcoin is our discretionary income. It is important to always delay investing in Bitcoin if you don't have a discretionary income because Bitcoin is a long term investment, and you need discretionary income to invest in Bitcoin so that you won't have any difficulty in holding your Bitcoin investment for a long time. But if you use because of time is ticking and ignore using discretionary income to invest in Bitcoin, that means you are investing in Bitcoin with the money meant for your expenses and that is FOMO, and you won't be able to hold your Bitcoin for a long time.