A loss of confidence
When my postdoc left I really lost a lot of confidence in my ability. Although not directly connected, I saw having a postdoc as a ticket to publishing quickly. In addition, the postdoc was serving as a lab organizer and mentor for the younger students, freeing up my time for grant writing, writing papers from my postdoc and generating research ideas.
I spent much of the end of December on vacation with my family moping about the "tragic loss" of the postdoc from my lab. My husband was annoyed by my melodramatic turn, and kept pointing out that tons of new faculty don't even have postdocs, which was helpful, but I still came back feeling a little down. And, for the first time since I started my job, I wasn't excited about going to work the next day. Most of this is fear of the unknown. I am not sure how good my new grad students will be. I am not sure if I will be a good teacher. [My first lecture is tomorrow.] I am not sure if my lab will be successful. I am not sure if I will have time to write grants, giving my new mentoring and management responsibilities. I am just not sure.
Sometimes I feel like a child playing dress-up, and it doesn't help that many people mistake me for an undergrad. But despite all this doubt, I am confident that I know my stuff. I am sure that with enough work and effort we will get this lab of the ground, and gosh darn it...we will publish something.