I used to plan and run a family service where the children would help lead worship (songs) and some adults would help by participating in a skit to engage both young and old alike, sharing a spiritual truth. The service seemed to be well received.
After holding these types of services for over a year, about once a month, there was some discussion about them. One comment that came up was that if people were going to be in the skit, then they had to know their lines. 
There were a few times when it was apparent that the actor did not know their lines, and even though in other services, other actors forgot, or missed entire lines, they were able to move forward without drawing attention to that fact. So it was these few times where it was very obvious. It seemed as if the people calling for actors to know their lines were calling for perfection, or at a minimum, excellence, but what there were calling for in a word was … commitment.
The irony, these people did not express a desire for the children leading worship with motions to have this same standard. The children were seen as performing and even if they did not do all the motions, or know the words to the song well, this human attribute of imperfection was accepted. But I digress…. that is a message for another post.
The point is, people were crying out for commitment from the people volunteering for these roles. (1 Corinthians 10:31)
There are times when the church believes that everyone should serve in every place there is a need. When we place people in roles that they are not suited for, have a passion for, or sense God’s call to fulfill, then we get people who will not learn, or know, their lines. They will not have the same commitment level as one who senses the urgency, the impact, of the ministry they are serving. They are like the hired hand in John 10 who runs when there is trouble. They do not have the commitment to the task at hand…. they don’t know their lines.
Are we seeking commitment from others yet not learning our own lines as we serve to “fill spots”?
Paul tells us in 1 Corinthians 12 that we are members one body. We each have a specific role to fulfill, and to work together. The foot may not “know the lines” of the hand because it is not meant for that purpose. The eye may not “know the lines” of the ear because it does not have the “calling” to hear.
May we each find the role we are to serve and learn our lines well. If you find yourself in a role you may not have been called to serve, then do the best you can for our Lord, learn your lines the best you can, though you may not remember them all. May we always do all we do for the glory of God.