There's no point in consistently worrying about everything. What will happen will happen regardless. So breath, look on the bright side. Have some laughs, fall in love, accept what you can't change, and carry on. To actually live is courageous. Most People exist.
In life we do things. Some we wish we had never done, some we wish we could replay a million times in our heads. But they all make us who we are, and in the end they shape every detail about us. If we were to reverse any of them we wouldn't be the person we are. So just live. Make mistakes, have wonderful memories, but never second guess who you are, where you have been and most importantly, where it is you're going.