Is. 41:10- "Fear not, for I am with you; Be not dismayed, for I am your God. I will strengthen you, Yes I will help you, I will uphold you with My right hand." (NKJV)
In the verse above, God is speaking to His people, Israel. God tells them not to fear their enemies, not to be dismayed by their enemies strength. God promises to strengthen Israel, to help Israel (to exercise overwhelming power on Israel's behalf), that He will supply Israel with His own strength. How does God back up His claims? Simply by stating that He is their God.
Why would this reminder of who He is be proof enough to Israel that He will do as He promises? History.
When seeking someone to do business with, you would seek out a trustworthy partner. To find such a partner, you would ask people about who they had done business with in the past. Through these inquiries, you would learn who has a good reputation, based on past actions. An honest man gains a reputation for honesty; one who produces quality work will never lack for customers willing to recommend him. His past behavior is a good indication that his honesty and performance will remain at high levels in the future.
Israel needed no other people to inform them of God's track record concerning the keeping of His promises or of using His power on behalf of those who trust in Him. God had a history with Israel. In verse eight, God reminds them of this history by referring to them collectively as Jacob, their ancestor who God protected from Esau and his men. God reminded them that they were of the seed of Abraham, to whom God gave promises concerning his descendants. God called Abraham His friend. Then God brought to Israel's remembrance how God had chosen them and brought them into the Promised Land. By reminding Israel of all that He had done for them, Israel could count on God to fulfill His promises to them.
When we first begin to walk with the Lord, we have yet to learn to trust Him fully. As time goes on, and if we are obedient, He makes His promises real in our lives. He works out situations we thought were impossible. And then, as God establishes a track record with us, we begin to trust Him more and more, until total trust in Him is achieved. But this cannot happen unless we allow Him to take control of our lives. If we refuse to operate in God's strength, then we prevent a personal history of God's deliverance in our lives from being established. Then when circumstances seem overwhelming, that lack of history makes us just as fearful as those who believe in no God. This is not what God had in mind for His disciples. Not only does He not want us to fear, but He wants us to have a public testimony regarding his power and willingness to use it on His childrens' behalf. Not to have such a testimony in our lives is an indicator that there is sin somewhere in ourselves.
The difference between Wesley and the Moravians during the storm at sea was that the Moravians had such a history in their own lives; they were able to remain calm, knowing that they were in God's hands. Wesley, who had no such history with the Father at that time, could do nothing but fear for his life. Later, after walking with God, he could face hostile mobs while declaring the gospel. The stakes are high regarding this issue. Not only for ourselves, but for others who need to see Jesus reflected through us.