I'm sorry if you have been offended by what you call "overzealous Christians"—ones who perhaps weren't as loving or sensitive as they could have been. The Bible instructs those of us who are Christians to "Let your conversation be always full of grace, seasoned with salt, so that you may know how to answer everyone" (Colossians 4:6).
But the real issue is this: Can we know God and His will for our lives? Or are we destined to wander through life with no sure knowledge of God and whether or not He cares for us? In other words, is your guess about God just as good as the next person's—or can we know for sure what the truth is about Him?
The Bible says we can know God—and if that is true, it makes all the difference. How is this possible? It is possible, the Bible says, because God has chosen to reveal Himself to us. He did this in a way that staggers our imagination: He became a man, Jesus Christ. Do you want to know what God is like? Look honestly at Jesus—and when you do, you will discover that God has not left us in the dark!
Knowing God is the greatest discovery any person can ever make—and that's why Christians can't keep it to themselves! Don't let your desire to run your own life, or anything else, keep you from Christ, but open your heart and mind to Him without delay.