Fix my interview crisis....

I have come to the conclusion that my interviewing skills really suck, so much to the point that I am failing my interviews. This is not allowing me to move forward with my career and instead is having me stuck at my current job. So time to brush up on my interview skills. A co-worker who used to be a hiring manager told me to always be positive in an interview no matter what, and always be part of the team. After talking with her, it became apparent that my answers to some questions were hindering my progress in getting me towards the goal of the hospital. So I'm asking your opinion on certain questions that are difficult to answer. For example the "Tell me your weakness" question. I have never heard a great answer to this question. My exchange goes something like this:

Tell me what is a weakness of yours?
Me: Well I find that hard work can also be a weakness for me. It is tough sometimes knowing when to do the hard work, or to let go and let others around you help. And that being said, I could always use help with my documentation.
I was told to rephrase the words I am trying to say, to not make it sound like I am so much better than the rest of the team. While I am no better than the rest of the team, I am a very hard worker. And while other people are sitting around and doing "story time", I'm busy working. And I sure don't want to come across as "better than everyone".
I will also need to focus on positive answers in every situation. Perhaps it is due to my experiences in nursing, but generally I find more negative situations than positive ones. People who do not want to do their work, that sort of thing.
Thoughts?
Tell me One of your weaknesses....I am a strong independent worker. Responsible and Self sufficient and efficient. I am able to take on tasks and accomplish them efficiently and in a timely manner which can also be a weakness as I sometimes tend to take on too much when I can easily delegate these tasks. I tend to have the same expectations of others that I have of myself. Rarely I can become frustrated with others. I have learned to engage my co-workers and I have found that when we all pitch in together it builds a solid team.I find an area of growth that I am always improving as I gain more experience is my documentation. (personally I would leave this out)Always lead with a positive.

"Tell me your greatest weakness""I overprepare for standard interview questions."

Don't say "I work too hard" or "I am a perfectionist. "They can see through that a mile away. Actually give them a true weakness, and then tell them what you're doing to overcome it.For example, I said that sometimes I get disorganized and bogged down by too much email, and I forget to respond to people. So I told them that I was overcoming it by making and using lists on a daily basis, and it has really helped.

It's the verbage. I don't know that I would use your statement for your weakness, the being a hard worker. That should be a strength. You could say "At times I take on too much and have a difficult time with delegating or asking for help". I've done plenty of interviews as I used to be in management. If I got a resume with spelling errors, etc. I immediately pulled that person out of the running. If you don't care enough to fix something that is supposed to spotlight you then you probably lack initiative. Definitely don't be late. You can tell a lot from a person's body language. Smile, keep eye contact. Don't immediately jump to answer. Dress conservatively and don't show up with a lot of makeup or bling. Definitely don't come off arrogant or as a know it all...seems like common sense but you'd be surprised. Confidence and arrogance are two very different things. The people I hired were those who were eager to work/learn and exuded confidence and an excitement for the profession. Have several cover letters and resumes with you just in case you are interviewed by a panel. I would recommend practicing with someone as well...someone who will offer you an honest critique.