What are these scriptures trying to tell us about happiness/joyful?

1. Matthew 13:44

"The kingdom of heaven is like treasure hidden in a field. When a man found it, he hid it again, and then in his joy went and sold all he had and bought that field."

2. Luke 8:13

"They on the rock are they, which, when they hear, receive the word with joy; and these have no root, which for a while believe, and in time of temptation fall away."

3. Luke 15:7

"I tell you that in the same way there will be more rejoicing in heaven over one sinner who repents than over ninety-nine righteous persons who do not need to repent."

Thanks,

4 answers

1. The kingdom of heaven is a treasure worth more than material goods.

What do you think the other two verses mean?
Well, I think for Luke 15:7, it means that even if a person committed a sin,he/she can bring joy to people? T_T I don't understand the other one...
The only way the sinner can bring joy to people is to repent.

2. If a person is not rooted in Christianity, he will forget the Word and sin.
But how does these verse give real meaning of happiness? :S