Self reflection is a very normal thing to do. The trick is not to overdo it. Analyzing yourself, and thinking about the things you do and how to improve them is a very important thing, one that drives us forward, towards the better. But sometimes, we over do it, and the reason behind that is that we feel anxious about being liked and accepted by those around us. We reach a point in out thoughts where we're afraid of being alone, and that's very normal. Therefore, we overdo introspection.
Anxiety can really take over our mind, heart, and soul. We have to consciously step back and think, "Do I need to think about this right now?" "Can I do anything about this right now?" If you can't do anything about it at the moment, then it may be best to get your mind off the subject at hand for a bit. :)
You find yourself over analyzing everything because your life matters to you. The things around you and their outcomes mean a lot to you. This isn't necessarily a bad thing. You just have to remember that things happen sometimes without a completely understandable reason and while this is hard to accept it will not change. It is hard to get used to, but it will be okay. Deep breaths, buckle up, and try to enjoy the ride a little more.
We commonly over analyze situations due to do not have enough control of our emotions and anxiety. To get in control of it, a great start is be focused on yourself, be confident and put your focus and energe in one thing at the time, live one day at the time, on step at the time.
But also remember that changes takes time and you will have to repeat it as long as you need until you get the control.