Weariness-in-well-doing is not a sin, nor is it a sign of anything other than our humanity. Therefore, to keep your people motivated to care for and minister to the needy, you will want to do several things:
1. Vary the stimuli: photographs, bulletin promotions, pulpit announcements, posters, inserts, and personal testimonies. Bring in a leader from the affected area to talk to your people. Send one of your leaders there. Rig up Skype interviews for worship services.
2. Give the people a break from promotions. In mountain climbing, even the best athletes need level places to rest.
3. Celebrate small victories. Give your people a sense of joy over the team that just returned, the house that was built, the number fed, the money raised.
4. Create secondary goals (on the way to the huge one) and celebrate each accomplishment. When Israel was rebuilding the temple, they paused to enjoy a victory lap after only the foundation was laid (Ezra 3).
5. Constantly refresh the spiritual dimensions of the work. Ask the Lord for new insights and applications from Scripture, for a fresh word for your sermons, for greater dedication. Keep your people praying. Find variations in ways and places to pray. Prayer-walk affected areas.
6. Change the entire approach. If you've been feeding the hungry in a devastated area and your people are tiring, consider swapping assignments with the group building churches or restoring homes.
7. Rotate workers and leaders as much as you can. Everyone gets tired, no matter how committed. Jesus said to the apostles, "Come aside by yourselves and rest a while" (Mark 6:31).
8. Recognize that people need nourishment, fellowship, worship, and laughter. Growing up on the farm, we did not work all the time. Sometimes, we cut a watermelon under a shade tree or went swimming in the pond.
9. Combine your effort with other nearby churches. Get your people together for sharing, fellowship, and prayer.
10. Do not hesitate to close down one ministry—even if it is not complete—when you believe the Lord has changed your church's assignments. After all, the Lord has a lot of people who are available to Him for ministry, and no one has to bear the entire burden.