Have you ever had a 360-degree evaluation? Take advantage of it. Keep it concise, in the range of 1 to 2 minutes. Ambition and established objectives are important, but if you're too specific, you run the risk of setting goals that can't be achieved within the position you're being interviewed for. Answering this question doesn't mean giving a complete description of your resume, or your entire life story, treat it as a brief presentation to the interviewees about why they should hire you.
You should leave the impression that you've learned an important lesson, ideally one that's relevant to the position you're interviewing for. When interviewers ask this question, it's a genuine way to learn about your flaws and see how you approach them constructively and how you're dedicated to improving. Be honest and transparent: everyone has flaws, interviewers won't expect or want a potential candidate to be the best article, as long as you show that you can recognize your weaknesses and that you want to work on them. Rehearsing your answers will help you to transmit your skills and abilities with confidence, which in turn will help you make a big impression during the interview.
This may be your first interview since you left the military, but even if it isn't, the interviews can be overwhelming. This is much more than the 90 seconds that many researches claim are actually needed, but it means that there's a lot of pressure to provide impressive answers during the introductory phase of the interview. Then, mention a little bit about your past, related to the skills and experience you gained in that position and the skills relevant to the job you're interviewing for. Once you've prepared how you'll answer each of these questions, you should practice your interview technique.
This is one of those questions that most people hate and wish they could avoid, but for the most part, most interviews start with this question.