We ought to obey God rather than men.
You may have the most expensive car on the road, but if you don't know how to take the wheel, or apply the brakes, you're in trouble. Sure, it's nice to let others do the driving from time to time, but, spiritually speaking, that puts you at the mercy of their direction, their values, and their goals.
God has given you the map. It's your responsibility to follow it! No matter how timid you are, don't allow anybody to dominate you, or tell you where to go. Get back into the driver's seat of your life, and take the wheel, for only you know where God has told you to go!
Too often our actions are dictated, not by a sense of purpose, but by a need to please. We care so much about what certain people think, that every step we take, we look over our shoulder, to see whether they're smiling, or frowning.
Hear this clearly: your first responsibility is to please God, not people. In the end, you're accountable to Him alone (Romans 14:12).
Listen, "You shall have no other gods before me" (Exodus 20:3 NIV). You say, "But I don't worship idols." You do, when you dedicate your life to impressing people, instead of obeying God.
You ask, "But who am I to assert myself?" Who are you not to? You're a child of God, and as such, your first responsibility is to please your Father. Your second, is to live your life to the fullest!