What you’re really selling is your personality. They’ve got all the credentials they needed; your date heard about you through a friend, your interviewer already saw your CV, that’s why they decided to see you. They know about you. So don’t talk about yourself, talk about them. Ask questions or show them you also did your research by casually mentioning similar interests. 
As date or interviewee, your job is to make them want you. Boost your perceived worth by demonstrating your greater qualities, rather than just stating that you have them.
Tell stories. Nobody wants to listen to someone boast. Instead, talk about that time faced some seemingly insurmountable task, and succeeded. Or even better, tell a funny story about failing, and what you learned from that. Your ability to learn is attractive, to friends, potential bosses and lovers: Of the people who upset us, it’s those who learn from their mistakes that remain our friends.
So, go to interviews, and sell your personality. As it is.
If your personality is not getting you a job, change your personality. Turn up on time. In a suit. Smile more. Reflect on experiences, create hypotheses, and test them, changing your behaviour until they do work. Don’t be precious about it, your personality is just a collection of things you habitually do.
Another similarity between dates and job interviews: 
Never listen to someone who claims to be good at them. The only way to be good at things is by doing them many, many times. Like dating, if someone is doing lots of job interviews, they’re terrible at interviews, or they’re interviewing for the wrong jobs.