Accumulated stuff and responsibilities. He doesn't pay the same attention to God he once did. Doesn't call on his family to grow in their love for and service of the Lord. Allows his sense of moral right and wrong to waver. Moves back to Palestine.
Stuff happens and spiritual passion fades.
You experience the death of someone particularly close to you, and in desperation you reach out to God and the assurance that this person is now with Him - faith comes close. But 6 months down the road, you're back at work and the routine pushes heaven behind the clouds. But the months come and go. Or you lose your job and sink into depression. The work comes.