Do you need an example or are there some written for you already?
Friendship is the beautiful thing which fits and ties two people in good relationship.
Friends are the ones to whom we can share everything. Friends are the ones with which we can abide freely and happily.
Friendship is gift by God which do not let us alone. Friendship is really an amazing thing.
They also help each other when they are in trouble or are hurt.
Friends are people that can be looked up to and trusted.
I think it is D. King doesnt believe people are so set in their ways that they cant accept a peaceful future.
Mood, and tone would both fit greatly, because if the writer is in a mad mood for example, then he is not able to express something romantic in his book, or something happy. Hope that this would help you! =)