Power
It may not seem terribly obvious, but your job is about as powerful as it gets. Allow us to explain: you're helping families in a time of major transition. Any move can be a big ordeal: but an out-of-state or out-of-country move can cause a much larger amount of stress than simply having to find a new apartment across town. You can't completely remove that stress, but you'll get rid of as much as you can.
Sure a new opportunity is exciting, but change, especially a big move, is always a little daunting. There's that whole fear-of-the-unknown thing which causes some people to completely melt down. Not only are clients facing a new work situation where the dynamics and office politics are at least somewhat unknown, they're also having to say goodbye to friends and possibly family in order to start over. They're giving up comfort for a chance at bigger and better things.