I guess it depends on a combination of several factors.
In my case, I didn't really work in pharmacy at all before school. I went to a school that exposed me to many different aspects of pharmacy, including nuclear. This allowed me to do an internship between my 3rd and 4th year, where I gained a lot of great experience. I had an extremely varied final year of rotations (the least of which was in retail). Finally, up til 2 months ago, I went straight into nuclear pharmacy, gaining a very good reputation for my efficiency and ideas which led me to a job in corporate. My experience in my classwork, internship, networking, and a whole lot of blessings and good luck allowed me to go straight out of the gate and be pretty confident in my abilities and be successful.
However, that could have EASILY been totally different if I went into a different field. If I was in community/retail, I am pretty sure I would have killed someone almost immediately. I BARELY had any experience in that, just due to how the whole rotations worked out. I think the culmination of my community rotations was a Target that did about 150 prescriptions a day, outpatient pharmacy for the main hospital where 90% of the people that came in were getting free drugs (therefore no experience in dealing with insurance bullshit), and another outpatient pharmacy in another major hospital that did the same thing.
So basically you will get that 'critical mass' of exposure/familiarity that will lead to confidence eventually. Sometimes (like me) you get extremely lucky and you get exposed to the right thing for your future career while you're in school or very early in your career, which makes you much more able to contribute immediately. Other times you just have to grind it out. But it will happen!