A. The answer depends on your risk tolerance. The key is to build a portfolio with returns and risks that match your tolerance.
There are two schools of thought here -
1) Passive Investment
When market falls, it is not time to stick your neck out and run against the trend, just shadow the benchmarks and wait it out until the way forward becomes clear.
2) Active Investment
When all asset classes' price fall, it creates an opportunity to buy because of mispricing of some asset classes. For example, when oil price falls bringing down the entire market, companies that benefit from lower oil prices might be good buys if their prices also go down with the overall market.
What kind of investor you are or want to be?