If you are from the youth that are suffering from fluctuating faith take a good look at what you do in your solitude, who your friends are and what your day amounts to. Where do your eyes wander? What is filling your ears? Spiritually intoxicating intake is destroying your chances at appreciating faith. There will come a time when your heart will be completely incapable of spiritual replenishment and even the mention of Allah, the afterlife or the Prophet SAW will agitate you. Allah changes the hearts but at the very least you need to change your environment.