“Does Job fear God for nothing?” Satan replied. “Have you not put a hedge around him and his household and everything he has? You have blessed the work of his hands, so that his flocks and herds are spread throughout the land. But now stretch out your hand and strike everything he has, and he will surely curse you to your face.”
Job 1:9-11 (New International Version)


Satan said that if God put Job through a hard time he would stop believing, curse God, his prayer life would cease. If God puts us through a hard time should we stop believing? NO.
Just because life is hard at one time and you cant see God helping you or working around you, it doesn't mean that prayer is worthless. If nothing else prayer confirms your relationship with God. If I pray in the hard times, that says. "Lord, you are still in control, I still trust in You and believe in You. I come to You with my life."
If prayer ceases during the hard times, or you question prayer working, that is an error in your faith. You cannot believe in God and not be in prayer trusting that God hears and works in it. There are many verses in the bible that speak of prayer. Never negative, always in a positive way. It works, whether you see it or not.