Good stuff, all. I've been doing this since 1991 and it never fails to amaze me the crap we can get into. I felt the same as most, that I didn't know anything right out of the Academy. The bad thing was, we don't have FTOs in out small Dept so I rode with the Chief for a week of midnights then got turned loose by myself. What an eye-opener that was!
One of the most important things to have in Law Enforcement is common sense. If you have a good dose of that, you should do OK.
Another important thing is the ability to deal with people, even if you want to kill those people. For instance, we recently had a domestic where the boyfriend beat the girlfriend with a long-handled shovel. He was one of those that wasn't going to jail, either. I managed to keep him talking until my back-up arrived, chased him after he ran from us, fought with him when he resisted (rather spiritedly, I might add!), dealt with thim when he trashed and flooded the jail cell then had to deal with him after he came down from whatever he was on and calmed down on the way to the hospital for medical evaluation before being taken to jail. When he came down, he actually wasn't that bad but you need to be able to set all the stuff that happened before aside when things like this happen. I wanted nothing more than to put my G23 up to his head and pull the trigger but, as you know, we can't do things like this.
Probably THE most important thing is to be able to leave work at work and not take it home with you. I only live about a mile from the Station but routinely drive my POV to work. This lets me go drive around for a little while after work and "decompress" before I get home. Makes the home life with the wife and kids a lot better this way.
Good luck on your career. Just look on it like the old Marine Corps recruiting slogan- "It's not just a job, it's an adventure!"
Bub