If doubt and faith co-exist as fellow travellers on the journey, if it's not "either... or" but "both... and", then in those times when doubt has taken the lead we can make one of two choices: walk away from faith altogether, or push forward in perseverance, knowing that faith is not far behind.
"Though the fig tree does not bud and there are no grapes on the vines, though the olive crop fails and the fields produce no food, though there are no sheep in the pen and no cattle in the stalls, yet I will rejoice in the Lord, I will be joyful in God my Saviour". - Habakkuk 3:17-18
Did you notice the word "yet" in the above Scripture? In the stillness after the long, hard cry... remember that word. "Yet" has to be one of the most hopeful words in the English language.