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A faith that is based on anything other than personally knowing the Lord is easily shaken and will not survive the enemy's efforts to get you to doubt.
Isaiah 28
15 Because ye have said, We have made a covenant with death, and with hell are we at agreement; when the overflowing scourge shall pass through, it shall not come unto us: for we have made lies our refuge, and under falsehood have we hid ourselves:
16 Therefore thus saith the Lord GOD, Behold, I lay in Zion for a foundation a stone, a tried stone, a precious corner stone, a sure foundation: he that believeth shall not make haste.

All the great holy men recorded in the Scriptures knew God first hand and their faith was unshakable.
Deuteronomy 10
12 And now, Israel, what doth the LORD thy God require of thee, but to fear the LORD thy God, to walk in all his ways, and to love him, and to serve the LORD thy God with all thy heart and with all thy soul,
13 To keep the commandments of the LORD, and his statutes, which I command thee this day for thy good?

There is no substitute for knowing God, if you want to have a strong and invincible faith.
Faith based on knowing God for real is invincible and is the victory that overcomes the world.
1 John 5
3 For this is the love of God, that we keep his commandments: and his commandments are not grievous.
4 For whatsoever is born of God overcometh the world: and this is the victory that overcometh the world, even our faith.
5 Who is he that overcometh the world, but he that believeth that Jesus is the Son of God?

All who walk with God will have a faith that is unquenchable and unshakable.
Mark 9
22 And ofttimes it hath cast him into the fire, and into the waters, to destroy him: but if thou canst do any thing, have compassion on us, and help us.
23 Jesus said unto him, If thou canst believe, all things are possible to him that believeth.
24 And straightway the father of the child cried out, and said with tears, Lord, I believe; help thou mine unbelief.

Anyone who puts his trust only in a creed, a set of religious doctrines, a belief system or his own personal logic will have a faith that is easily shaken and he will become fearful.
2 Peter 2
19 While they promise them liberty, they themselves are the servants of corruption: for of whom a man is overcome, of the same is he brought in bondage.
20 For if after they have escaped the pollutions of the world through the knowledge of the Lord and Saviour Jesus Christ, they are again entangled therein, and overcome, the latter end is worse with them than the beginning.
21 For it had been better for them not to have known the way of righteousness, than, after they have known it, to turn from the holy commandment delivered unto them.

Therefore, seek to find and to know God yourself firsthand. Stop depending on other people or things to keep you in the faith.
Don't be a second hand Christian.
Get to know Jesus for real.
Deuteronomy 4
29 But if from thence thou shalt seek the LORD thy God, thou shalt find him, if thou seek him with all thy heart and with all thy soul.
30 When thou art in tribulation, and all these things are come upon thee, even in the latter days, if thou turn to the LORD thy God, and shalt be obedient unto his voice;