When Paul said, "I was not disobedient unto the heavenly vision," he meant that there's only one acceptable response to God's plan - obedience! Partial obedience, selective obedience or delayed obedience are still all disobedience. William Carey, who is considered the father of modern missions, gave up comfort and fortune to go to India and introduce the gospel. One of his more memorable quotes is: "Expect great things from God; attempt great things for God,'' but you can only say that with confidence when you know what God has called you to do. What He ordains, He sustains! When you set your own goals you lack a heartfelt confidence that God is doing the work, so you wear yourself out thinking it's all up to you. However, when you know God has given you a vision for your life, you trust Him, even when you can't see any way to bring it to pass.
When God gives you a vision: 1) It will interrupt you. Sometimes God will speak in a voice you can't tune out. Other times, like Jonah, God will let you go to the bottom to get your attention. Either way, things won't go right until you say 'yes' to Him. 2) It will illuminate you. You may not like what God says. Ananias didn't like going to pray for Saul of Tarsus, a man with the power to put Christians to death. But God said, "Go, for he is a chosen vessel... I will show him how many things he must suffer for My name's sake" (Acts 9:15-16 NKJV). Notice the word 'suffer'. The devil isn't going to send you a congratulatory telegram because you have decided to do God's will, so be prepared for attack. 3) It will inspire you. You will accomplish things you never dreamed possible.