Contagions within the classroom and church

Within the classroom emotion is contagious. 

If the teacher is excited, then they will display enthusiasm, which is then observed by the students, which then increases their enjoyment, thus raising their engagement, which is observed by the teacher, which then increases their level of excitement...

Alternatively...

If a teacher is unenthusiastic, then they will be sluggish in their lessons, which will be observed by students, which will decrease their enjoyment, creating disengagement, which is observed by the teacher, lowering their enthusiasm for teaching the class...

This equation is true both within the classroom and the church.

Just as enthusiasm is contagious at school, spiritual fevor is caught by the congregation.

Just as boredom infiltrates all within the class, spiritual lethargy spreads throughout a church.

When I think of many ministers, I wonder how many realise the contagion they are able to spread by their very presence and enjoyment in what they are doing.