There is a common thread to much ministry burnout and it is leaders going above and beyond their original assignment.
You take a Christian worker who loves the Lord, and has high expectations of 'what God will do'. Make them a key decision maker carrying major responsibilities. They will prove themselves highly committed, heavily involved and willing to take on a demanding workload.
They will also, with great regularity, ratchet up.
Ratcheting up simply means you take the assignment (.. as the Lord has assigned to each his task. 1 Corinthians 3:5) you are sure 'God has given you' and you add to it. In this one area discernment often seems to be neglected.
While working you also see something else worthwhile to be done. You add it to your to-do list. You see a need here and a cause there to be addressed. Few step forward to help. And you do it ... and do it ... and do it.
Pretty soon you are doing more than the original assignment. You have 'ratcheted up.' And you may be on your way to ministry burnout and the signs of career burnout that are so common to any leader who is experiencing significant stress.
You become resentful of the task and critical of the people who have not volunteered. A gnawing ache develops in your gut and unwanted attitudes invade your thinking.
The cure? Know so well what you 'have been called to do', that saying 'No' to what you have not been called to do will be much easier.
In other words, know your priorities so well, that you say 'No' to those requests, no matter how good they are, that are not absolutely yours to accomplish. (If it isn't an absolute yes, it's a no.)
This is not to take away from doing what you have been assigned with excellence. Excellence is about depth not quantity.
Saying 'no' may allow others to step up and take responsibility, giving them the joy of seeing good things happen that are attached to their efforts and faith.
If the priorities and assignments all seem to blend into one and you find it difficult to sort them out, you may need to work with a life or leadership Coach for a period of time to gain some perspective.
Many people have been robbed of useful service because other well meaning Christians, most often leaders, have taken the task to themselves. If it is important, then God has prepared or is preparing the worker.
You are not the solution to every need.