The short answer you want to give is: “Well.” While you probably don't want to literally say that, the idea is to convey competence to deal with difficulty and hopefully pressure is not a problem for you. Frankly, this question tends to come with high-pressure, stressful jobs or companies and they want to know whether you’ll be able to handle tough situations. Hopefully you have self-selected into this kind of job and applied to the company and role with your eyes open about those realities and believe you can thrive in an environment that demands a lot of you.