If we're Christians we should live godly lives. That generally leads to happiness but that happiness depends more on our relationships than anything else. A lot of Christians are unhappily married. A lot of Christians have difficult relationships with their relatives or their children because those people aren't saved or they aren't godly. Or they have health problems or they have loved ones that have them.

I've been a Christian for 40 years. I've had a lot of difficulties. I wouldn't say that my life has been happy but I do have joy. Joy is a fruit of the Spirit.