If you are feeling vulnerable, keep going. This feels contrary to logic, we innately feel we should protect ourselves from oncoming danger. While this is true for the physical body, the spiritual practitioner is quite different.
Dropping your defenses
When we are defensive we are protecting our identity in some shape or fashion. This identity is the false illusory version of you. Everything that encompasses you, your personality and all of its traits are the false version of you. Defensiveness requires resistance, this also requires effort, sometimes a tremendous amount of effort. The more force we resist with, the stronger we enforce the identity.
Half way there Vulnerability is a perspective that suggests something could be lost, damaged, or compromised if you don't defend it. And that is exactly true. Your ego is the entity that could possibly be destroyed. That is why vulnerability is an excellent spiritual practice. However vulnerability suggest a negative tone of loss. When you go deeper with surrender you will find you do not view it as reducing your power but giving you more. Life, God, the universe or whatever you may call it requires your faith and Surrender to let it operate through you. This power of surrender enables life to pick you up and lead in ways you could have never imagined in your mind. This unfolding life makes the experience much more pleasant and keeps you present, which is one of the cornerstones of spirituality. So when you are feeling vulnerable, you are half way there, when vulnerability changes to empowered faith, you are then living in harmony with life.