Summary: Never run from an opportunity to minister because there are adversaries. It goes with the turf.
1Cor 16:9 For a great door and effectual is opened unto me, and there are many adversaries.
When God opens a door for you, it will also lead to many adversaries. Many give up when there is resistance to their ministry. Why do we expect less? In a war for every attack there is a great chance for counter attack unless the enemy surrenders. We have a defeated enemy, but he will not surrender until Jesus comes and he is bound in a pit for a thousand years. Even after that, he will not admit defeat for when he is loosed again he will fight one last battle before being cast into the lake of fire forever.
Look for victory in what God gives you to do, but expect the enemy to be the enemy. It might just be some harassing flack or a full force attack on what God has called you to do, but press on. When God opens the door it is going to be an awesome thing, but it may not be a walk in the park because this world is a battlefield.
Put on your armor expecting resistance. Don't run. Battle when the Lord leads you to fight and when He wants you to see Him battle just stand and watch. Victory is assured because the war is over, We are just doing mop up duty with pockets of resistance, Maranatha!