The main reason of losing chess games.
Many chess players loses tons of games without knowing WHY and HOW it happened , maybe you are of them and you are here to find a solution for that problem , so okay I will give you the response and solution.
Let's imagine that you are playing a game so first you will play a normal opening moves to control the center of the board, develop your pieces to an active squares , get your king to safety by short or long castling ; I am sure you heard this repetitive Speech many times in your early stage of learning chess so what is something special that I can give you? of course nothing LOL , well let's be serious so you are just finished your opening stage and we can say that your opponent did the same as you, now all the miner pieces are developed the 2 kings are safely castled and maybe the rooks are connected , What will you do in the middle-game? probably your Reply will be I will make a plan to exploit my opponent weaknesses or to create a weakness in his camp, Great I will ask you a BIG QUESTION did you ever look at your opponent half-board and imagine that you are playing in this opposite side and ask what is the possible plan for my opponent and How he will play this position , Many people would say NO I had never ask such a question this is simply the main reason why many chess players loses many games because they play just from their point of view and did not look at many opponent's moves and suddenly the position became difficult to play because their opponent gain a decisive advantage by exploiting their carelessness of his moves especially his positional moves , we need to remember all the times that chess is a game of 2 players if you are playing a game you are not alone there is someone in front of you who had an equivalent skills as you and if you have a plan of course he have too , so what may create the difference between you and your rival is that you need to be familiar with your opponent's plan and possible continuation before playing many moves some people may say this is well known idea and it is called calculation , NO this is not calculation because calculation happen exclusively in a sharp tactical position but the important thing is that before getting to a sharp position How the previous moves are played and how the position became critical and that is because one of the players overlook some seemingly inoffensive moves from his opponent and suddenly his position became difficult to play and so critical and probably losing so the possibility of making a blunder become big , an other question may come to mind is that what if the 2 players played well and paid all the attention to each others plan? the response is that the game will end in a draw , and that is what happened in the last World Chess Championship 2018 between Magnus Carlsen and Fabiano Caruana in all their 12 Classical time control no one managed to win a single game and the match decided later with Rapid time control... to be continued...