Just my two cents. An example of how I think about these.
1. First, you need to have an idea of how much you need for your
core needs. This would the basic necessities such as food, utilities etc...etc... when you retire.
2. 2nd, You need to have an idea of how much you need for your
non core needs aka wants. This would be for example, travel, luxury good and services, etc....
3. Third, You need to match the specific needs to the specific funds. Example you need a very stable fund for your "Core Needs" so no matter there is market drop by 50% or whatever, your funds are not affected. These could be in for example SRS bonds or CPF Life funds etc....
4. Fourth, You would then match your "No Core Funds" to other specific funds. These could be from your Stock portfolio or other non stable funds. When the market is down , you can decide not to touch these funds and when the market is up , you will withdraw this depending on how your decumulation strategy that you have. E.g You can decide when market is down you decide to withdraw 0% but rely on another fund that is earmarked for "No Core Funds" when market is down or you can decide to withdraw from the stocks but at a lower rate instead of 4% only 1% as you decide to ramp down the non core needs during this period.
Before you come up with your decumulation/retirement strategy. I would suggest you read up on concepts such as "sequence risk" to understand how to plan for retirement and decumulation of your funds.
The above seem simple to do, but requires a lot of thought and the plan/strategy is an evolving one that you keep on revising even during retirement.
The last one is your behavior or how you react during bad or good times in the market and knowing your/family expected lifestyle.
Hope my two cents helps . These are basically my views only, not saying the best way to do it.
