Just take a deep breathe and exhale. Try to live in the moment, the actual moment. Be present because you don't know what's going to happen in the future, good or bad. You're not a fortune teller and your best bet is to live your day present in the moment.
Past experiences already happened. They are to be left in the past and not to be dwelled on.
Do some simple breathing / meditation exercises if you want to relax.