In everything we do, we need to know our boundaries and what we're capable of. You might be able to lift a car off your screaming child, but its probably not in your regular wheelhouse of abilities. As my mother might say, "Butter might not melt in your mouth" which is a Southern way of saying that you're both a smooth talker and a little removed/distant at the same time, or you might be the type that sits down for eight hours, wakes up, and marvelous things are done.
Whatever it is that you do well, you need to know it, and you need to be able to convey that to other people. Sometimes we don't know think enough about it ourselves to have the list readily at hand. So the first step in the process is finding out the good stuff. Note: this can't be your own compilation alone. We often think, for example, that we hide how dry the turkey is at Thanksgiving every year like a champion, when everyone knows that your lips pucker with each bite and you drain three glasses of water. Our perception of ourselves is a good place to start, but not the last place to end. Put together a list of what you think you're good at for whatever reason--since this is a blog about management and work, you're probably going to want to start with your competence in those arenas--and then go over that list with people you trust to be honest with you but not in the "break your spirit with honesty" sort of way.
While you're at it, you might want to solicit what they think of as your weaknesses and compare their list to your own mental list. Its hard to hear your best friend explain that you can be a "bit bossy" (trust me, she's been kind enough to tell me when I've asked), but its better to hear it from her than third hand from a potential employer who indicated that was feedback they got from a reference.
Now you have the good and the bad. Put the story together. For purposes of work, this is how you got to where you are now, the ups (mostly) some downs (because people to whom you tell this story aren't going to believe there were never any downs), lessons learned, and plenty of examples. Try to find the humor in the overall pieces; people who laugh with you invest with you in the story you are telling. Try to find the honor in the story, for example, refusing to give less than two weeks of notice because despite the fact the new job thought you were a rockstar and wanted you immediately, you would never hurt your friends at a previous company that way. Try to find the humility in the story: I messed this up, but here's how I un-messed it up and learned the error of my mistake.
Now that you have an idea of the story, write it out, like you'd be writing an essay for a future employer or to your boss for a raise or to someone who doesn't know you...whoever the appropriate audience should be. When you're done, read it out loud. It's probably pretty dang long. Now, start cutting up your story. Break it into pieces that demonstrate specific things about you. Humility, honor, learning, etc. Take these sub-stories and make them fast, easy to remember, and remember to provide examples of your life and your choices in them. Now you can string them together, if need be, or target any specific part of your story, if need be. Interviewers or HR folks are rarely going to have time to hear the entire story of you, but you need to know it. It adds to the confidence in all the smaller stories you can tell about yourself. It answers the questions people will have about you and the story you are telling.
Let me just say for the record here: don't lie. In the words of Abraham Lincoln: "No man has a good enough memory to be a successful liar." The story of who you are is made up of memories you already have and can lean on; you don't want to make up additional stuff you have to remember, that will be less reliable than the truth.
By the same token, you don't need to tell the whole truth to everyone, all the time. For example, the fact you hated your boss in one job with the passion of a thousand fiery suns is the truth, but not necessarily one you need to share in the story of your work experience. It leads to other questions, and other stories about why, which may have truthful answers, but which cause the listener to start drawing conclusions of their own about you. In the world--let alone the work world--it is easier to assume that someone with a grudge is the actual person with the problem than the person against whom you have the grudge. There are very few things you can say to prove things otherwise, and often trying to do so will simply make it worse. There are a large number of truths out there like that. If asked directly, be honest, but if not asked directly, pick a different story to tell.
The story will change and grow as you do. You'll swap some anecdotes out with more successful ones, with funnier ones, to ones more appropriate to a specific instance; but you'll always have all the stories to choose from, and they'll always be true. Because you know the stories (and the entire story they make up), you'll be able to follow any line of questioning wherever it may go and answer honestly.
The reason I recommend knowing your story, especially in a blog about management, is that you're going to need to tell parts of it throughout your career. Mostly to other people, but sometimes to yourself. When you're picking an employee up who just fell down, and you are dusting them off, they need to hear about a time when you did the same and things got better. When you're talking to upper management about defending a decision you've made, you can use a story as evidence of how you've made such decisions in the past, and that they can trust your judgment as a result. When you're talking to a screener on a phone call, hoping to get to the next part of the interview process, you aren't off guard: you have what the political arena call "your talking points" and you know what you're going to say so you are less nervous. You also know instantly if this is the right opportunity for you or not, because you know your whole story, the good and the bad, and whether or not this opportunity is a good fit. Further, you can tell the appropriate parts of your story to the screener or interviewer so they can understand if it is a good fit or not.
Finally, it never hurts to know yourself a little better. In the work world, we often take a moment to look at ourselves at review time, or when we're looking for work, but rarely at other times. Taking the time to know your story and the stories that make it up is so worth it; the returns are endless for the entirity of your career, but also for your general peace of mind. No one is going to follow this advice and achieve zen management master, but hopefully being able to clearly communicate to yourself and to other people about yourself will make your work career and management life a lot easier.