I recall approaching transitions with apprehension for most of my life. In 3rd grade I was afraid of the 6th graders that would be the new 'bosses' when I moved up to 4th grade. When I was in Girl Scouts in 5th grade I remember writing that I was worried about keeping up with homework in junior high. And in junior high I was worried about homework in high school. During my senior year of high school I was extremely anxious about choosing the right college and I put off making a decision until April 30th, even though Small Friendly College had been my first choice all along.
At some point in college I began to realize that I'd spent most of my life getting myself overly stressed out about everything- presentations, essays, tests, etc- but yet it always worked out. I couldn't think of a time when I'd just totally, completely screwed up academically. I thought about all of those times when I'd been worried about my ability to handle the homework load or academic intensity or whatever. I was always anxious about it beforehand, but by the time I got there I was ready. I started to relax a bit, and I found a new kind of confidence in myself- I knew I was capable- I was no longer trying with the looming fear of failure.
Beginning grad school last year was a big transition. When I graduated from college, it was difficult for me to imagine being ready to go to grad school. I had little idea what I wanted to do in life, let alone how grad school could get me there. Over the years in between college and grad school, I gradually came to an understanding of where I wanted to go in life and a variety of experiences prepared me to apply and (thankfully!) get accepted. Last August found me feeling surprisingly prepared to start grad school, but Jon said I was the only one who was surprised. Like all of the earlier transitions, by the time I got there I was ready.
I still have several (four? five?) years before the next big career transition. I've had some doubts recently about what I want to do, and occasionally I look at the job of a professor and think How could I possibly do that? But for the time being, I'm not going to let myself get too stressed out about it. I'll just keep on keepin' on and I think by the time I get there, I'll be ready.