I am with you (cf Ps 23:4, 121:4, 118:6, 56:11, Isa 41:10, 41:13, Neh 4:14, 1 Sa 12:20, 21, 22,)
It is worth noting that statements like this remind us that Paul was not "Superman," but a man just like all of us. Yes he was an apostle and supremely gifted, but he was still a human being and had feelings including fears like we all have, especially when we begin to take a stand for Jesus.
Beloved, while Jesus spoke audibly and personally to Paul, He speaks no less audibly and personally to us in His living and active Word. Do not forget that when the Bible speaks, God speaks. That is truth you can stake your life on. Indeed, He Himself promised "lo, I am with you always even to the end of the age." (Mt 28:20). He is in us (Col 1:27) and His Spirit, the Spirit of Jesus [Acts 16:7], the Spirit of Christ [Ro 8:9], is in us to enable us and empower us to take a stand for Jesus and not remain silent but speak out (cf the source of boldness in the early church in Acts 4:31).
Remember the words of John that "You are from God, little children, and have overcome them; because greater is He Who is in you than he who is in the world." (1 Jn 4:4) And in Hebrews the Lord promised “I WILL NEVER DESERT YOU, NOR WILL I EVER FORSAKE YOU,” so that we confidently say, “THE LORD IS MY HELPER, I WILL NOT BE AFRAID. WHAT WILL MAN DO TO ME?” (Heb 13:5-6) Do you believe Him? Then "go on speaking" and "do not be silent" about Jesus. The world is dying and going to an eternal hell and we have the only message that can rescue them into an eternal heaven!