The moment someone chooses to trust in Jesus Christ, his sins are wiped away, and he is adopted into God's family. That individual is set apart as a child of God, with a sacred purpose.
If you tell God no because He won't explain the reason He wants you to do something, you are actually hindering His blessing. But when you say yes to Him, all of heaven opens to pour out His goodness and reward your obedience. What matters more than material blessings are the things He is teaching us in our spirit.
God has ways of shaking the world when He is at work. He literally caused the ground to quake when Jesus died on the cross.
God's plan for enlarging His kingdom is so simple - one person telling another about the Savior. Yet we're busy and full of excuses. Just remember, someone's eternal destiny is at stake. The joy you'll have when you meet that person in heaven will far exceed any discomfort you felt in sharing the gospel.