Chirag R.’s Answer
One part is your skill associated to the job ...The other key aspects are
Your Attitude, demeanor, communication skills.
If you come in with a bad attitude, or are unable to clearly articulate your strong points and value you bring to the table, that may be a negative.
If you may not have the best skill set but are willing to learn and confident and hungry..I'd hire that person.
Before every interview, prepare the subject especially the weak areas and then focus on soft skills aspect stated above. If you fail, dont let that discourage you, there will be many chances ahead and point is to get better.
Good Luck !