Is it a blunder? Improve it!

We all know what's a blunder right? But why do we keep blundering? Underestimate an attack, miscalculations, fatigue or plainly you don't know? Again a blunder is a critically bad move or decision. A blunder severely worsens the player's situation by allowing a loss of material, checkmate, or positional advantage. It is usually caused by some tactical oversight, whether due to time trouble, overconfidence, or carelessness. So now you know "why?"
How do you know if it's a blunder or leads to a blunder or a position that is not so playable and your opponents keeps you inactive and within a losing position but in professional level game an inaccuracies and mistakes are much considered as a blunder to what the effect can it later bring in a position of a game. So "the how" is determined on the results of the game.
When do you know your having a blunder? Most times we may identify or simplify a move or a piece as a blunder but in some cases it's a trap or tactical move for a better position or mating sequence but few are hard to find and may not even consider a blunder in the naked eye which happens in over the board(OTB) games or tournaments nationally or internationally even in world championship matches so it happens anytime anyplace as there were a saying "if you see good move find a better one" but because we are not mostly a mad genius we tend to play carefully and strictly within the principals. When is a blunder then? Well in actual game the feeling and intuition kicks in when your in bad position or forceful mating sequence and you either you win, lose or draw? For a very strong player or professional player they have one thing in common "SELF ANALYSIS " After every games regardless of the results they tend to analyse their game see any blunders or minor inaccuracies which is I find it very hard to do and in order for one to improve dramatically is to know how to analyse and understand the game. Nowadays we having a more easier way to know which not help to understand but rather memorize the position which may not help in a longer time format I paste below a certain game where my opponent blunder on move 17 and I took advantage of it which my opponent took a different route and ended in a mate rather than a material advantage. Hopes makes a reader understand and improve on a more ameture understanding.