You don't have to make a single choice as when to buy, the best strategy is to spend small amounts and spread the trades, for instance if you buy every week for 100$ while the market is crashing you can make sure that you are not putting all your money on one go...
This could actually be better than just putting it all in when the prices dip because you get more value out of your money as the prices continues to dip. I might try to employ this strategy in the future.
Maybe you mean about buying during a sharp decline in prices for a while and waiting for the price to return to better or exceed your desired prediction. It becomes something you believe in to see the good. Although everyone will think about the losses that are pictured in the head.
This is more about buying with slots while the market is declining, when a crash happens it does not happen in on hour but it takes time, during the this time you don't know if the price will continue to drop or it will bounce back so to avoid betting on one shot you spread your trades over the declining period....
However I do have a question, could we apply his strategy for selling too? I mean let's say the market started bouncing back, should we sell in slots? example I have 500 tokens. The value of my tokens are now +60%. Should I sell 50 tokens and wait for the market? If it increases more and I am at +120% I sell 50... If it gets +200% I sell 50.. the if it crashes I have already secured 150 tokens for an average gain of +70%. I know that most of you prefer seeing +10000% but to be honest I prefer small gains good liquidity then big risks and big losses....