It is natural for a person to sit back and think about his current life situation and possible ways to get over problems. But if the process of thinking happens all the time or a situation or problem is constantly being thought of in all possible angles and possibilities and it ends up making you feel anxious and stressed, then it is being overthought of. Overthinking is a widespread problem in today’s time as every other person seems to be overthinking a problem or life situation.
One of the major factors responsible for overthinking is the lack of decision-making skill. When you are not confident about taking a decision, it delays the entire process of reaching a conclusion and that stretch of time is spent in overthinking the same event/problem in your mind. It's because you are not able to reach a decisive point where you can tell yourself, “Ok, this is it. This is what I have to do to tide over the current situation and I know I will”.
Many a times, it so happens that inspite of having taken a decision, you keep feeling that you have made a mistake; maybe you should have waited to consult someone or maybe you should have gone ahead with the other alternative that you had in mind. So, you see, when there are so many “may-be(s)” in your mind, you will constantly be torturing yourself with the same thought. Do you worry too much? Or do you feel that it’s better to think and be prepared before ahead for a problem/situation that might just crop up out of nowhere, as life is unpredictable? So, you are constantly worrying and anticipating trouble and that does not help your mind to relax.