You can get better, but it will take a whole lifetime of training. You might not ever be able to get past a certain point. But, you still have years and years to get better.
Set an attainable goal. My goal is to someday become a 1600 player. That is considered advanced level and it is possible to reach it over the course of a lifetime.
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Many suggested a different thinking process or other ways to notice blunders. Unfortunately, this isn't really feasible, or I would be doing it now. This is why I started the thread; I thought perhaps some people just aren't mentally capable of employing these processes.
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Why don't you think this is feasible? You should think of thought process as a skill. Learning how to think in chess is like learning any other skill, such as learning how to play guitar. You can read books about it but you won't actually improve until you start practicing the skill you want to improve at.
Thought process is very important. In Kotov's Think Like a Grandmaster building blocks of the thinking process are calculation, positional imbalances, and planning. You see imbalances, determine who is better, by how much, and why, then formulate a plan based off the center type, piece distrubition and activity, imbalances, etc. Then your plan drives the calculation. Find the best plan, not the best move.
In a position with a lot of contact between pieces calculation comes to the forefront, but even here we calculate until the end of the forcing variations and make assessments at the ends of lines.
You could calculate to a quiet position with 100% accuracy but still not be convinced that it's best due to a gap in one's evaluation knowledge. Happens to me in some exercises and games =(