If you want to succeed in anything you must stop doubting and believe.
Read: Ephesians 6:16, John 20:27.
16 In addition to all of these, hold up the shield of faith to stop the fiery arrows of the devil.
27 Then he said to Thomas, “Put your finger here, and look at my hands. Put your hand into the wound in my side. Don’t be faithless any longer. Believe!”