I wouldn't short a stock unless I was very confident it would go down, because if I'm wrong there is no theoretical limit on my losses, unlike being wrong about a long position.

Notice that the thing you need to be very confident about is that it will not go up dramatically. Having a high probability of staying stable or only raising by a small amount isn't a problem.

Assume at some point you have reason to believe that you have information that the market does not and which creates a moderately small possibility of a stock dropping value dramatically. Also assume that you have a limited tolerance for risk. ie. You're willing to invest $10k based on the expected value calculation but would accept no chance of losing more than that. In that case you can short sell the stock and also buy call options at a higher valuation (or just use a 'stop order'). That way you gain when the price drops and lose when the price rises but the losses are limited to a predetermined maximum. You can then crudely visualise the payoffs as just similar to betting on a horse you think will win. You will probably lose a small predetermined amount but if the horse wins you win a lot.