Why is the book of James in the Bible?

Let me be very clear that I acknowledge that God is in control and the Bible is His book.  I just don't understand why the book of James is even in the Bible.  It seems to contradict so much of what the rest of the Bible says. 
 

Take these verses for example.

James 4:9-10(NKJV)

Lament and mourn and weep! Let your laughter be turned to mourning and your joy to gloom. 

Humble yourselves in the sight of the Lord, and He will lift you up.

When we accept Jesus we should lament, mourn, weep, and be gloomy?  That will make God happy?  That is what God wants us to experience when we accept Jesus?

That doesn't square with a lot of what I read in the Bible.  How about Romans 5:3-5?

Romans 5:3-5(NKJV)

And not only that, but we also glory in tribulations, knowing that tribulation produces perseverance; 

and perseverance, character; and character, hope. 

Now hope does not disappoint, because the love of God has been poured out in our hearts by the Holy Spirit who was given to us.

God tells us to take glory or be joyful even in our tribulations and yet James tells us that we need to be gloomy to please God.  Who you going to believe?

Or how about this one?
 

Proverbs 16:20(NKJV)

    He who heeds the word wisely will find good,      And whoever trusts in the Lord, happy is he.

Here is an article that lists 21 Scripture quotes about being happy.

http://www.jollynotes.com/2013/05/02/bible-verses-about-being-happy-joyful-cheerful-being-happy-with-what-you-have-being-happy-for-others-enjoying-life/

Oh well, another one of those things to ask God about when I get there.