It's a question every investor will have to answer at one point or another: What do you do if one of your stocks sees a big drop in value? Do you wait out the downturn, double down on your thesis or cut your losses and sell? Making the wrong choice means losing money. Staying in risks further losses, while getting out risks missing out on a recovery.
There's obviously no one-size-fits-all answer to this question, but you can make your decision easier if you start by answering a few questions. First, why did the stock decline, and does that reason reflect on why you bought it in the first place? Let's say you bought a company because of its high dividend yield. If the dividend is cut, that's a reason to get out, especially if there's not another equally compelling argument in the company's favor. Obviously, dividends can be raised after being cut, but if your investment is already underwater, it could be a risky bet to hope that happens for you. A good investment rule of thumb is that if your thesis no longer holds, sell. There's no shame in admitting an investment didn't work out, and rebalancing is a healthy part of portfolio management.
As a corollary to the first question, look at the company's history. If it has been around for a while and has a proven ability to adapt to changing circumstances -- if it has a record of reinstating dividends when times improve, for example -- take that into consideration. The recovery potential of a stock like that is different than the prospects of a start-up with less of a track record.