Happiness is a subjective construct. However, as one obtains more truth, the depth of the experience and its independence from outward circumstances increases. Those who experience an outpouring of the Spirit of God experience a new depth and intensity of joy:
...he has poured out his Spirit upon you, and has caused that your hearts should be filled with joy, and has caused that your mouthsshould be stopped that ye could not find utterance, so exceedingly great was your joy. (Mosiah 4:20)
These feelings are a foretaste of the experience those who are reconciled to God experience after this life:
And moreover, I would desire that ye should consider on the blessed and happy state of those that keep the commandments of God. For behold, they are blessed in all things, both temporal and spiritual; and if they hold out faithful to the end they are received into heaven, that thereby they may dwell with God in a state of never-ending happiness. O remember, remember that these things are true; for the Lord God hath spoken it. (Mosiah 2:41)