A ship does not sit at dockside day upon day waiting for the rudder to tell it where to go — no… a ship must first “go,” then the rudder can tell it when and where to turn. Isaiah prophesied, “Your ears will hear a word behind you, saying, ‘This is the way, walk in it,’ whenever you turn to the right or to the left.” (Isa. 30:21, NASB).
This demonstrates to us how doctrine met with obedience births a certainty of experience. As Jesus said, “You shall know the truth and the truth shall set you free!” Or. “If anyone wills to do His will, he shall know concerning the doctrine, whether it is from God or whether I speak on My own authority.” (John 7:17, NKJV).
In other words, faith proves itself as we exercise it.
Once you have decided to act upon the mandate to share the gospel which God in Christ has given you, once you determine to “Rise, go Forth, and Follow” you need not make decisions regarding what to say. The Holy Spirit will be as faithful in your testimony as He is promised to be in your defense: “When you are brought before synagogues, rulers and authorities, do not worry about how you will defend yourselves or what you will say, for the Holy Spirit will teach you at that time what you should say.” (Luke 12:11-12). We must only make ourselves willing and obedient servants.
Speaking of taking initiative, even initiative against drudgery, Chambers notes,
…we have to take the first step as though there were no God. There is no point in waiting for God to help us— He will not. But once we arise, immediately we find He is there. Whenever God gives us His inspiration, suddenly taking the initiative becomes a moral issue— a matter of obedience. Then we must act to be obedient and not continue to lie down doing nothing.”
Find the gift that is yours. Not all testifying is verbal, not a great deal is even evangelical preaching, rather it is the “one beggar telling another beggar when he found bread” sort of thing. The “where the rubber meets the road” kind of sharing. It is telling what you know from your experience of walking with the Lord. It is, as John wrote, that “…which we have heard, which we have seen with our eyes, which we have looked at and our hands have touched—this we proclaim…” (1 John 1:1).