Focus on briefly describing the challenges you faced in your last position and spend more time on how you worked through the challenge. The interviewer wants to see that you have the mental toughness to work through workplace issues and won't leave the agency when faced with a challenge.

"At my last position, the major challenge I faced was understaffing. The unit I worked in faced a 30% budget cut, and we lost a lot of staff. However, our client base increased, so my coworkers and I had to work longer hours and mandatory overtime every other weekend. After three months, my supervisor was permitted to increase the staff by 20%, which helped with the caseload. I worked through the challenge by keeping myself healthy and getting plenty of rest to keep my stress levels down."