Ricardo - read George Muller's biography (Christian Heroes of Faith: Then and Now Series)

It's a short read and I highly recommend it as it depicts the life of a man who came to fully trust in God. Time and time again Muller's life depicts how God is faithful and is more than able to answer prayers as no task is to large or small for Him. I have been personally challenged in my prayer life after reading about how George Muller trusted in God was ultimately able to affect the lives of thousands, and every single penny was an answer to prayer.