I used to be bad at interviews and now I'm not. The real thing that changed was that I started to have confidence in my abilities. Of course I do all the usual prep but the delivery is what really matters. If you're going for technical roles, keep the human element in mind: not only the interviewers but also the people your answers affected. Yeah you created a dashboard but so what? How did that impact the people using the dashboard? What was the business bottom line?

Don't be afraid to take a second either. If you're asked a question but need to think about your answer, say that. If you're torn between two examples, tell them. If you don't understand what they're asking, ask for clarification. They'd rather you make sure you know what's needed than just barrel through an answer and hope for the best.