If we start a sprint with a specific goal and the user stories to support that goal, then the business changes their immediate requirements during that sprint. This may be because of a client requirement or an internal 'emergency'.
For example, we start a 2 week sprint with a number of planned tickets to reach the sprint goal. After 3 days, the business approach us with a need for some functionality not in the current sprint. This is needed to appease a dissatisfied client. There is a requirement to abandon the current goal and set this urgent work as a new one.
How do we handle this? Do we fail the sprint and start planning again? Do we insist on finishing the current sprint and do this urgent work in the next one?