Never be lacking in zeal, but keep your spiritual fervor, serving the Lord. Be joyful in hope, patient in affliction, faithful in prayer. ~ Romans 12: 11-12
Left unfueld, enthusiasm cools down to fondness, which then fades into indifference and finally burns out with absence.
Our faith life can go through hot and cold cycles if we don't tend the fire. Have you experienced this lately?
The solution is to continue fueling your fire by adding prayer and service to your study time.
A quick devotion is great to start the fire, but prayer and serving others is what keeps it burning.