Investors, and the financial markets they're involved in, don't like uncertainty. Why? Because it's extremely difficult to try to predict the future. If the majority of the Brits who head to the polls decide to stay a part of the EU, then nothing will have really changed and the financial models that investors have built will remain intact.
But what if most decide they'd rather have a future without the security of the EU? What then? Well, that creates uncertainty.
For instance, what will happen to all of the trade deals that are in place? What impact would this have on corporate profits? What about the bond markets, or the debt that is tied to the European Central Bank? Long term, will other EU countries follow Britain's example? The list of questions goes on and on.
So what should you be doing to protect your life savings from the Brexit vote? Actually, you probably shouldn't be doing much at all. If you are properly diversified, with a majority of your securities in the U.S. markets — and with limited exposure to any one country — you should probably sit tight for now.