As a Pack Leader, it's your goal to bring your dog to a place of calm, submissive energy. It's not about your dog. Everything begins with you, your energy, your state of mind, and your approach. You are the source of your dog's calm, submissive state, and your dog is looking to you for guidance.
If your energy is anxious, nervous, overexcited, angry, frustrated, or some other negative, your dog will reflect that energy. If you are inconsistent in applying your rules, your dog will test you to see what she can get away with. But if your energy is calm and assertive and you are consistent in teaching and enforcing your rules, you will earn your dog's trust. She will follow you and look to you for guidance.
If you're having trouble finding calm, assertive energy in yourself, your best tool is your imagination. Think of someone (real or fictional) who embodies calm, assertive energy, and then imagine that you are them. Carry yourself the way they would walk and see what effect this has on your dog.
Another tip: Expectation creates outcome. So, for example, if your dog pulls on the walk, imagine yourself walking with him next to you and imagine how it feels. What is your state of mind without having to constantly pull your dog back? How much more enjoyable for both of you is the walk this way? Try to create that same feeling during the next walk.
Start simply, and build on each successful moment. The more often you succeed, then the more confident you will be in continued success and the less discouraged by a setback. And remember this: You are not the only one who wants to succeed at reaching a calm, assertive state and achieving balance with your dog. Your dog wants you to succeed, too.