I recently was in a similar situation and knew that I had to give something up. I was being stretched so thin, I wasn't able to do any of the things well. It affected me and those I minister to. All the things were good, involved ministry (most of them volunteer), and were things I liked. Choosing what to give up wasn't easy.
To make the choice, I did several things.
- First, I took a look at the gifts and abilities God has given me and compared them to each of the things I was doing and looked for the one that least used those abilities.
- I also took a look at what I am passionate about. Asked the question, if I could only do 1 of these things, what would it be? If I could only do one more, what would it be? Which of these things am I least passionate about. That helped me to prioritize the ministries.
- Then I looked at effectiveness. Which one of these things am I least effective at? If I continue, will I become more effective or less effective? Is it fair to the others involved for me to stay in this ministry if I am not being as effective as I could or should be?
It didn't take too long to determine which ministry to step back from, and I took the hard step of actually doing it. As a result, I have additional time to devote to the other things and have seen positive results. The ministry I resigned from is still going well and has adapted quite well to my not being there. If the ministry had stopped as a result of my leaving, I still would have made the right choice. A ministry that is dependent on me is not a good ministry-proper ministries depend on God. If God wants the ministry to continue, he will find someone else to fill the slot.
One thing you might consider thinking about is what quality will you be able to give to the teaching if you take this class full time. If you take the class full time, how will it impact your teaching in the other sessions?
Is God clearly leading you to take on the extra teaching or is it more your desire for the class to continue? I've found that when I've taken on extra classes out of my desire rather than God's clear direction, I wound up frustrated and even began to resent the class. In that situation, no one wins. The children didn't learn what they should, and I lost the joy of ministry.
Saying "no" to a ministry opportunity is ok. A couple of hours ago, I had to say "no" to an opportunity to minister to a group of children in a few weeks. It wasn't easy, but necessary. It won't do any good if a current ministry suffers because of an additional ministry I'm taking on.
I didn't plan to write this much, but I hope it helps.