studying Endgame first, or Openings.

  Based on what was said above, I am now convinced that the biggest change a relative beginner should be looking for is their process of thinking. 

  Regardless of how good one is in the opening or ending, they will lose quickly if they fail to transform the way they think during a chess game.

You feel that one can conclude that a player was hoping for the best case-scenario if the game ended in a blunder in less than 20 moves?

In all that "logic", I do not see a reference to hoping for the best case-scenario.

 Of course, or sometimes castling too early and offering a juicy target to the opponent. Or, and this goes against learning general principles, not getting the bishop out simply because of the  ‘knights first, then bishops’ principle, which is overruled  many a time in various openings. 

  First look at the way you yourself think during a game. Asking questions without inquiring into the process is futile. I don’t feel anything, it is so. Any obvious blunder has the same root in this flawed thinking, which prevails among lower-rated players. You asked many questions, now it’s time to look and see for yourself.

In all of your #217 comments, I do not see a reference to hoping for the best case-scenario.

  If you do not see an obvious fact, even after being pointed out, which is different than discovering it on your own, there’s nothing we can do.

 Some day, when your powers of observation will increase, maybe, who knows.

On the other hand, studying endgames are also equally important because lots of beginners don't know how to use the king as a weapon. There are lots of endgame strategies that are vital in the path of chess mastery, such as the opposition, Zugzwang, slow progression, and checkmating with two bishops, etc. Beginners overlook a lot of these strategies and learning these things early can really help you as you continue to follow the way of chess.

 And yet the thinking process is the most important change for a relative beginner.

  You do not see it because you are doing it yourself! Therefore, watch yourself during a game, and pay close attention to the process of selecting the best move possible under the time constraints you’re playing. Start there. See how you yourself are selecting the moves you are playing.

Since post #204, has there been a troy7915 sentence that mentioned hoping for a best case-scenario?

Offhand, I would say that I do not see a post #217 comment referring to "hoping for the best case-scenario" because it isn't there. I guess everyone can come to their own conclusion about that.

Dear, you are a 1500 player, you are doing it yourself, by default, and this is the main reason for both your losses and your wins. Again, get familiar with how you yourself are selecting what is supposed to be the best move.

  Bring us any game you played, and you will see how that process works. Any game you ever played, the process of selection is based on the same principle: an avoidance of the most dangerous reply by your opponent and your survival reply to that reply, and so on until the position is quiet.

 At this stage you are not aware of how you are selecting a move. So forget others and start with yourself.

From a rating, you feel that you know that a player is hoping for the best case-scenario?

I would start to study endgames first. In the endgames you can´t correct mistakes and you learn what your peaces can do or not, also you learn how to coordinate them.

Who is doing this supposing?

Do you have some reason to rule out the idea that a player is making what he or she considers to be a reasonable effort to try to avoid the most dangerous reply of the opponent and be able to make a survival reply and so on?

To 226: It has nothing to do with feeling anything. It is so. It is the only reason a lower-rated player loses or wins games, not openings, nor endings. The point is not whether you are hoping for the best-case scenario or the second-best, or the third-best.. The point is that you are not considering the most dangerous reply by your opponent along with your reply to that reply, before deciding what move to make, consistently, on every move you make.

 At lower ratings, the thinking process is not orderly, and it is chaotic, impulsive, dreamy—it does not follow a simple, rational structure of finding the best move. By the way, this structure then can be applied to study openings, endings, and every position you are presented with.

 This minimum of 1.5 moves of calculation, which Soltis pushes it to 2.5 is just a minimum; it really depends how many moves it takes to reach a position in which there are no more obvious threats, in a particular variation.

  During the game, you are supposedly looking for the best move, only not, if you fail to consider either your opponent’s most dangerous reply to your proposed move, or your reply to that most dangerous reply to your candidate. Either one will both lose and win a game, at that level.

What I see is myself making what I consider to be a reasonable effort (both at the time and before the game) to try to enable myself to select the best move possible under the time constraints of the game.