I too have moments where I question whether God is capable to fulfill a promise, a dream or a prayer. I too have moments where the enemy speaks in my head that God cannot or my dreams are too big or too bold. I too have moments of doubt and uncertainty however, what my whole life has taught me is to Always Believe God's Word for My Life as He says, "I come that I may bring life and bring it abundantly." He also says He knows the plans He has for us. So, in your moment of doubt and uncertainty, believe God's Word for Your life. 

Love and His peace, 
PholosoYaMorena