After the interview, evaluate your performance. This will help you in future interviews. Consider the things you did well and the things you could improve on.
Each interview is not a win or lose situation. It is an opportunity for you to learn and gain experience for next time. Usually, you will not know straight away whether you have been successful in the interview or not. You will be contacted by telephone or mail so you just have to wait and see.
If you find your interview to be unsuccessful, make sure you still look at the experience positively. It was a learning opportunity for you.
Always ask for feedback from the interview, as the information you receive may help you with future interviews. Strangely enough, it may also make you feel better if you know you were very close in getting the job.
"Take from it what you can, and move on."