From the viewpoint of BELIEFS all doubts are disastrous. From the viewpoint of FAITH, doubt is the indispensable stimulant. To lose one's BELIEFS may not be a loss but a gain: an opportunity. "When the heart weeps for what it has lost, the spirit laughs for what it has gained," is an ancient Sufi saying. To lose one's FAITH, however, is catastrophic; the loss of this vital human constituent means mutilation, dehumanization, cynicism, nihilism.
The spiritual journey is one of continually falling on your face, getting up, brushing yourself off, looking sheepishly at God, and taking another step.