From a post by Stephen Altrogge which mentioned reasons why pastors can feel discouraged.
This one pretty much sums it up at the moment.
Unlike most jobs, pastoral work is never completed. There are no project deadlines and they can’t usually see tangible evidence of progress. The pastor’s work is only complete when he stops being a pastor, dies, or Jesus comes back.
On top of that, pastors are sinners working among sinners. Every day they confront deep, dark reminders of the profound sinfulness of men and women. A deacon in the church walks out on his family. A young mom is addicted to pain killers. A longstanding member is afflicted with brain cancer.
This means that pastors in particular are vulnerable to discouragement. They can feel as if their work doesn’t matter, isn’t making any difference, and will never end. They are vulnerable to the whispers of Satan, telling them they are a failure.
Read the whole post here.