That's great news! A second interview? That's serious and it shows that they are interested. This gives you time to get yourself together and present yourself in an even better light than the first time. Dig deep for that inner confidence, because I know you have it.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.