A job interview is a sales call. You want to convince the interviewer that you have what it takes to get the job done, and get it done well. Toward this end, it's important that you get comfortable being succinct and confident in articulating your skills, experiences, and strengths. However, it's important that you don't go too far and start touting your own virtues.
What's the difference? Skills are about what you can do. It's possible for you or others to objectively assess and quantify your skills and accomplishments. Virtues, on the other hand, are about what you are - specifically your moral goodness and righteousness. It's very difficult to assess a person's goodness, and it's almost impossible (if not completely impossible) to assess our own goodness.
It's been my unfortunate experience, that the people who talk the loudest about their own virtues are often the ones who ultimately prove to be the least trustworthy. I once worked with an executive (let's call him "Hank") who repeatedly said, "I cannot stand liars. I never lie, and I cannot stand to have liars on my team." I'm sure you won't be surprised to learn that in HR I had occasion after occasion to deal with Hank in situations where his employees said he had lied to them. I often felt Hank was lying to me. Many people left that company because they couldn't stand working with him. Last I heard his career was in shambles.
On another occasion I worked with a job seeker I'll call Greg. Greg's resume listed position after position where he had left a company because "my boss was unethical, and you know me - I'm an ethical person and I can only work with ethical people." As we dug into his work history and Greg explained each of his job changes, it became very apparent that his version of being "ethical" was suspect. It seems that every time Greg had a boss who held him accountable for the results he had promised, he decided the boss was unethical. Greg did land a new position eventually but I recently learned from a mutual friend that once again he is struggling with an "unethical boss."
After years of hiring and firing people, I've come to the conclusion that when a candidate or employee repeatedly espouses his own virtues, he is likely protesting too much. I hate to say it, but when a candidate tells me how honest he is, or how ethical he is, warning bells go off for me. On the other hand, if I am doing reconnaissance work on a candidate and objective third parties tell me how trustworthy or fair a candidate is, I sit up and take notice.
Therefore, a good rule of thumb in the workplace is to speak freely about your skills and accomplishments, but let others praise your virtues. Being honest, or being ethical are wonderful things to aspire to, but they are not things to say about ourselves. It is far more effective to focus our conversation on the work we are doing and how we are doing it and to let others praise our virtues.