The host has much to do with setting the tone of the occasion. If we would like people to enjoy coming to our home and visiting, if we want them to be happy and cheerful, then the host needs to set the tone. "Put on a happy face" was a theme that was prevalent some time ago. It is still a good theme if we want our guests to be happy.
Life deals us some unexpected blows at times and we may not feel very merry or cheerful. But we should have the strength of character to at least appear to be happy. Jesus made an interesting statement when He spoke about a person who is fasting. He said that the person should "put on a happy face" so that people will not appear to be fasting (Matthew 6:16-18). It is noble of a person who does not feel like rejoicing, to rejoice anyway for the sake of his friends and guests. We are responsible for the tone we set in our homes.