I'm going to recycle some material from a post I made a view years back. But basically, job interviews are stressful by nature. Most people, even normal folks, don't enjoy them. Combine this situation with a little social anxiety to compound things and...well...you find yourself in a bit of a bind.
I often found myself so nervous that I was struggling to remember my responses to common interview questions when I first started searching for jobs. It was frustrating. So I did what I could to mitigate my nervousness.
During two my best job interviews where I was actually offered the position, I was just super confident in myself and didn't care about the outcome. That prevented me from succumbing to anxiety and shooting myself in the foot. For the first job, I felt comfortable with the job description and believed I was more than qualified so if they rejected me, that was their loss and not mine. For the second place, I walked in knowing that I already accepted a job offer elsewhere so I was just there to memorize the questions they asked in case I decide to apply again in the future. Made no difference if they decided to hire me or not because I wouldn't accept the job offer anyway. This attitude really lifted the burden of social anxiety for me.
This attitude really worked for me as it calmed me down and allowed me to be me
so it may be useful. I wasn't a loose cannon. I still put in the same effort for my interviews. The difference was that I was more at peace with whether or not I was offered the position, so I ended up worrying less about what others thought and was able to show off more of my personality and talk about myself and my skills (because I was finally able to remember my answers lol). It sounds as though that may be happening here so if you're able to manage that nervousness a bit, then that may help you remember your responses in addition to potentially making your friendliness and personable attitude more prominent.
aqwsderf made some great suggestions and I actually do maintain a list of common interview questions as well. Craft some responses but don't try to memorize them verbatim. Use key talking points.
As for confidence, your grades are higher than the competition's so that must mean you know the material and can contribute to wherever you are applying. Do whatever else you can to boost your confidence levels. For me personally, I get a proper haircut/shave and then dress sharp for my interview. Makes me feel like how I imagine Tony Stark feels putting on the Iron Man suit.
Best of luck!