Unfortunately this is the risk one takes when investing. One can never be sure of the timing of one’s investment.

If you think Twitter’s stock is going down the drain, you’re probably better off selling it, taking you loss, and invest the money in something that shows signs of going up. No need to hold onto a position if, were you to invest today, you’d be short the stock.

But once again, no one knows if the timing is right, at the end it’s still gambling most of the time (particularly when stock picking).