To keep buying when market goes down every 10%, 20%, or 30%, the pre-condition is that you must have asset that has not been invested on the sideline. So, if you are able to buy at much lower level, by definition, you are not full invested at this time. Otherwise, you wont be able to buy when market goes down.
It all comes down how much you allocate what percentage of asset at a point of time, and how to mitigate different risk, and most importantly, have a plan for both directions of the market.
99% of people here, based on what I observe, only has a plan for the direction he/she thinks market will go. But has no plan in place in case market goes against what he/she believes.
