Faith is not to have a perfect knowledge of things

How ironic that some would have us believe our dedication to God is ignorance. On the contrary, the true believers are tested to not follow blindly, but are constantly questioning and seeking—they do not have a sure knowledge. We walk by faith with trust and hope. Contrast that with the self-assured who would deceive us and have us believe our path is folly. It is they, ironically, who are closed minded in their beliefs and lifestyles for they question not and seek not. It is the disciples of Christ who grow line upon line, from precept to precept, who rely daily on God’s goodness and mercy, who grow from grace to grace who are open minded and seeking for the truth daily, trusting that God will reveal. It is, ironically, our uncertainties that remind us that we are keeping an open mind and constantly seeking to add to the truth, light, and knowledge we have already received.

All things shall work together for your good

The ancient apostles walked and talked with Christ. They testified that He lived, but they also saw firsthand that He died and they knew it with certainty. How terrible to witness of that death and yet how important that they be able to testify absolutely that He died, for otherwise their testimony of His living again would have been questioned and doubted! God made to "work together for your good" the pain of the apostles' experience. God can make our pains and suffering serve high purposes, His purposes.

The Danger of Fear

Is it any wonder that we are commanded so many times in the Scriptures to not doubt and to not fear? Fear is a powerful weapon, for it can keep even the most capable individual on the sideline. Anger, commonly thought of it being powerful, can motivate us to irrational action, but at least it motivates us to action. Fear alone can keep us from acting.

Sample References
Jesus answered and said unto them, Verily I say unto you, If ye have faith, and doubt not, ye shall not only do this which is done to the fig tree, but also if ye shall say unto this mountain, Be thou removed, and be thou cast into the sea; it shall be done.—Matthew 21:21

And immediately Jesus stretched forth his hand, and caught him, and said unto him, O thou of little faith, wherefore didst thou doubt?—Matthew 14:31

Behold, I say unto you that whoso believeth in Christ, doubting nothing, whatsoever he shall ask the Father in the name of Christ it shall be granted him; and this promise is unto all, even unto the ends of the earth. ... And whosoever shall believe in my name, doubting nothing, unto him will I confirm all my words, even unto the ends of the earth. ... O then despise not, and wonder not, but hearken unto the words of the Lord, and ask the Father in the name of Jesus for what things soever ye shall stand in need. Doubt not, but be believing, and begin as in times of old, and come unto the Lord with all your heart, and work out your own salvation with fear and trembling before him.—Mormon 9:21,25,27

Look unto me in every thought; doubt not, fear not.—D&C 6:36