Our Scripture reading today is 1 Corinthians 16:6-9.
Verse 9, "For a great door and effectual is opened unto me, and there are many adversaries."
The Apostle Paul knew quite well that with opportunities came opposition.  It happened to be in Ephesus this time, but it did not matter where the Gospel was preached, there would be adversaries.  (Acts 19:1-20 is what Paul was referring to in 1 Cor. 16). The word adversaries refers to those who are in opposition to or standing against, to be set against.  
Praise the Lord for the many doors that have remained opened or been opened in 2020!  We have the freedom to meet publicly as a church and preach and teach the Word of God.  In addition to this, there are people we all know who are lost and without Christ and God gives us open doors to witness to them and or invite them to church.  Our missions team at Anchor is also an open door.  Praise the Lord for the opportunity to send the Gospel message across Canada and around the world.
Like in Paul's day, we have many adversaries.  These adversaries are in opposition to the open doors and are influenced by the Adversary.  1 Peter 5:8, "Be sober, be vigilant; because your adversary the devil, as a roaring lion, walketh about, seeking whom he may devour:"  There is no doubt that Satan wants to close all the doors of opportunity and he has many adversaries to assist in this task.
Adversaries from Satan:
1. Fear (of man)
2. Unbelief (They won't receive the Gospel)
3. Pride 
4. Stealing (Not tithing and giving offerings)   
These and many others are from within our hearts.  There are also adversaries from without.  May God help us to repent of any of these adversaries that we have allowed into our life and keep walking through God's open doors.