Second Guessing

I am the type of person who is very confident in myself and my abilities, but at a great cost. I am very quick to second guess myself and begin to hold myself to the highest of standards once I have achieved something great. This has been something that has defined me since I was a little kid. I have always been the one to be very humble and to want to get corrected or coached on things that I can improve on instead of praised for what I do well. This has its benefits and I believe is a very strong trait of mine. The downside is that I tend to overlook my strengths and areas that separate me from others and instead tend to focus on my pitfalls and beat myself up over them. I feel that it is very valuable to be able to accurately assess ones abilities and skills, but I need to be able take credit for things that I have accomplished and be comfortable doing so. I have never been comfortable accepting compliments and not sure If I ever will. This is all coming up because I have a very important interview this weekend and i am once again second guessing my purpose of going. My GF asked me the simple preparation question "why should we choose you over the other candidates". I immediately felt my heart rate increase and blood rush to my face. I ended up blurting out an answer to her, that was good, but overall was generic and did not accurately reflect why I am better than the other candidates. I feel as though this is because I have not been one to gloat about myself and instead I prefer to let my performances do the talking, but there comes a time where I need to be confident enough and selfish enough to be able to explain why I am better than the person next to me and what I do have to offer to the company. I feel that my ability to thrive in a team environment and be able to find ways to motivate those around me in order for them to reach there full potential is something that sets me apart. I am the kind of person that wants to personally succeed, but I truly want those around me to be successful as well and help them push themselves to their limit in order to attain their highest potential. But, is that enough to get me the position I want? I know I have more to offer than that and I have a few more days to think about it and prepare for the interview. We will see what happens. The trials and tribulations of a person who is confident on the outside, but secretly is insecure on the inside.