In seminary one of the most helpful and practical tidbits I received was to keep an encouragement file. In other words, we were counseled to hold onto encouraging letters and emails from members and former members. This "encouragement file" is a helpful resource especially during particularly discouraging days or spiritually barren times in ministry.
Yesterday I received a short and sweet card from a long time member. I particularly appreciated her last line as this is exactly what one hopes to accomplish as a minister of the gospel; (What a privilege it is to teach your flock how great and awesome our God is and to make much of the Lord Jesus Christ).