If you’re nervous because you think you’re bad at hard conversations, realize that it’s only a difficult dialogue to have when there’s a true discrepancy between what you feel you’re entitled to and what your boss feels you deserve. If this exists, you need to know about it regardless. Either your boss doesn’t find you as valuable as you believe yourself to be — in which case you should start looking elsewhere — or consider that maybe she’s right, and you have significant room for improvement. If she doesn’t comprehend the full scope of what you do and therefore doesn’t realize that you are being underpaid, give her the benefit of the doubt and the time to make it right.