Frustrated Witness?

When we hear the truth, do we readily accept it? Paul is on trial before King Agrippa in Acts ch26. He details his own conversion a nd mission in Jesus. Agrippa, who is noted as knowledgable in Jewish teachings, replies"Do you think you can make me a Christian so quickly"? Paul is a super witness, having met with Jesus first hand. He also met and lived with the disciples of Jesus, who witnessed his earthly life first hand. If Paul were to have difficulties in his witnessing to others, should we not expect difficulties? Does the fear of rejection or having questions we are unable to answer hinder or stop us from a witness opportunity? Did it stop Paul?