Romans 15:18

For. will not dare to speak of any things save those which Christ wrought through me, for the obedience of the Gentiles, by word and deed,

'For. will not dare to speak' -'Paul saw himself, in the scheme of things, as an instrument in the hands of Christ. He did not talk of what he had done; but of what Christ had done with him.' (Barclay p. 222)

'which Christ wrought through me' -'what Christ has accomplished through me' (NASV). Paul allowed himself to be used as Christ's instrument to bring Gentiles to obedience. Such was accomplished by preaching ('word') and the life that Paul demonstrated ('deed'). And there's nothing mysterious about allowing Christ to accomplish things through you. All you have to do is submit to His Will. (1 Corinthians 3:4; Romans 6:13; Romans 6:16) This means that if we find ourselves not accomplishing much for God, it means that we aren't cooperating with Him.