Paul, an apostle—not from men nor through man, but through Jesus Christ and God the Father, who raised him from the dead— and all the brothers who are with me.
Galatians 1:1-2 (ESV)
The calling of Paul's apostleship is inextricably linked to his relationship with Jesus Christ.
Being an apostle is bearing witness to the gospel's truth. The gospel teaches us that those who are in Christ stand perfect and complete, lacking nothing because of God's abundant grace. God no longer counts our sins against us because of what Christ Jesus has done through His finished work of the cross.
Salvation is entirely God's doing, not ours.
We can't do anything to add to our salvation. Everything from justification (our right standing in Christ) to sanctification (our right life through Christ) and even glorification (our ultimate conformity to Christ) rests on God's full and perfect work.
It is important to note that Paul was commissioned by Jesus and not by anybody else. This is why Paul is so adamant about spreading the gospel because he knew his life's purpose was to reveal the amazing grace of God. In the same way, Jesus has already called every son and daughter of God to be apostolic and prophetic in bringing the message of the good news to the world. That is why we are to go and proclaim that the kingdom of God is here.
The word apostolic refers to being sent by God. However, it does not imply that everyone should quit their jobs to become cross-cultural missionaries. Some may do so, but the vast majority of us remain connected to those within our reach and impact with the gospel of Jesus Christ.
When we adopt this perspective of being sent by our Father, we look for every possible way to show God's love to those around us, particularly those who have yet to hear and believe the good news of Jesus Christ. As such, pray for more opportunities to fulfil your calling to share Christ.