The last July 1st with any significance is after the last year of residency. At that point, a resident (AKA house officer, physician in training, indentured servant, scut monkey, etc.) completes his training and is board eligible. If you ever wondered what BCBE stands for, it's 'board certified / board eligible.'
Uniformly, residents discover that they have a limit to the amount of residency they can take. After a certain point in time, residency becomes intolerable. It is a continual nightmare having your judgment questioned continuously, and having your clinical decision making process derailed by someone who potentially knows less than you. In fact, most residents in their final year may know as much if not more factual medical knowledge than their superiors.
But practicing on your own is a different beast. There's no one questioning what you're doing, but there's also no one to offer advice or reassurance. There's no superior to appeal to.
It is an intensely isolating experience, and all those years of medical school and residency suddenly feel very empty. I thought that I was ready to be an attending when I was done with residency, but what I discovered was that there is no preparation for being your own doctor. At some point, you have to trust that you are right, and that can be hard to come by.
Advice to the new attending:
-Sometimes making any decision is more important than being right.
-Never let them see you sweat.
-Do not pull the 'Who's the doctor? You or me?' card unless you really mean it.
-Most importantly, trust no one.