Any specialty, be it medical/surgical, mother/baby, emergency, critical care has it's share of anxiety and skill set. It's absolutely normal to feel overwhelmed.
I started my career in critical care, and I'm still there. One of the most important factors in the successful transition from student to professional nurse is a nurse residency that includes support, mentoring, didactic and clinical learning experiences.
The best part of nursing is both the upward and lateral mobility.