Has God ever really disappointed you? Did you pray and trust Him to move in a situation and He didn’t? That can leave scars on our faith. Suddenly we don’t quite believe that He will answer if we ask. Maybe He answers other people, but not us.
It’s so hard to understand why some prayers are answered clearly and others not at all. Why did my friend die after I prayed and fasted for weeks? How was that possible? I prayed and believed with my whole heart. I was pretty broken up for a while, then I just had to believe that God has His ways and He doesn’t have to explain Himself to me. I’m sure there are reasons and actions that I don’t see that are beyond my need to know.
That doesn’t change the fact that He is God and His word is true. It is absolute truth. If we stop believing that, then we have no hope in Him at all. Either He is who He says He is and He loves us unconditionally, or He’s a liar. Let go of any disappointments you’ve been holding on to, any doubt that your prayers are useless.
Delight yourself also in the Lord and He shall give you the desires of your heart. (Ps 37:4) There is nothing that He won’t do for you if you trust Him and love Him. One day you will come to understand the other stuff, but now, trust Him, love Him. If you let go of your doubt, He will answer.