The students could be in the bad mood while taking lessons. Force them to play will not make them playing well even the kids often persist in not wanting to play. Let them just sit with no activity is also not the good solution. As teachers, what should we do so that the lessons can still be valued?

As my experienced, the following tips will help students in the bad mood feel better and improve their music knowledge.
1. Being Storytellers
a. Tell a short biography of composer and show his/her pictures since was child.

b. Tell a story behind the music.
For instance, Fur Ellise was composed by Ludwig van Beethoven and the original title was Bagatelle for piano in A minor. It was most probably dedicated to Therese Malfatti, his piano student in 1809-1810. Beethoven could be in love with her but this topic is still debated. Years after Beethoven's death, a researcher Nohl stumbled upon the autograph of the little piece when visited the Malfattis family. He misread Beethovens handwriting, he read Fur Therese as Fur Ellise. So its known as Fur Ellise. Unfortunately, the autograph is lost.
(Source: http://www.xs4all.nl/~ademu/Beethoven/#n21)

2. Being Piano Museum Guides
Let students look at the piano pictures from Baroque period until now, as if teachers are the piano museum guides and students are the visitors of museum.

3. Being Quiz Presenters
At first let students listen some compositions of the composer, for instance, Beethoven. For the quiz, let them listen a composition of another composer then ask, Is it Beethovens music or not?

4. Being Partners of the Game Players
Let students play the computer game that related with music. Teachers can play with them or just sit to see how they play.

5. Being Good Listeners
If students want to share their problem being good listeners, not judges. If we dont know the solution, turn to another topic. Sometimes, it's better not to talk about it such as the problem of kids that just lost their pets.

6. Being Good Supporters
If students cant play well or have slow progress, dont ever blame them with negative words such as idiot, dummy, hopeless, etc. It will put them in the bad mood. As known, Beethovens music teacher called him hopeless but currently most of us know him as one of great composers. If students want to give up, encourage them with positive words (words of encouragement). The encouraging words have power to change people life much better.