Stock markets have been very volatile in recent weeks. In August many traders are on holiday and relatively small changes can cause huge swings in prices. The jargon used in such a situation is "a correction", typically there might be 2 or 3 corrections in any year.
In the long term markets should recover. The BBC noted yesterday that the FTSE 100 had merely returned to the values of October 2006.
Over the last 5 years markets have been relatively un-volatile historically.
There is an upside to the current volatility, now is a good time to buy. It is also a good time for clients with regular savings plans as their regular £50/100 buys more units.