Why do I stay silent at work when I know what's right?

You already know the right thing. That is not your problem. Your problem is the gap between knowing and doing, and fear lives in that gap. It is worth being honest that the fear is usually real: speaking up can cost you standing, comfort, sometimes more. You are not a coward for feeling it. You are human. But notice what the silence costs too. Each time you go quiet against your own judgment, you lose a little trust in yourself. That quiet erosion is harder to see than the risk of speaking, but over years it weighs more. The question is not whether acting is safe. It is which cost you would rather carry. Start smaller than the thing that scares you most. Find one situation this week where the right thing is clear and the cost is survivable, and do it there. You are training yourself to close the gap, one honest act at a time.