Surrender to God means surrender to God completely. This is not easy because one fears that if he surrenders to God, the Lord is going to make him do all kinds of things not palatable to him (essentially, he's still holding onto his own will). But it doesn't work out like that. First of all, God would never want to instill fear in you. If he does, that would defeat his purpose of drawing you to him. Therefore, such fears are all self-imposed. Once you surrender and get to know the Lord, all fear begins to dissipate or vanish as your will begins to conform to his. And you realize how baseless your apprehension or worry has been.