How do blunders and mistakes occur

I am thinking most of my improvement will come from simply looking at all my mistakes and trying to avoid the blunder into the future.

 couple of things here 1) when oyur game is analysed it says "inaccuracies", 'mistakes' and blunders. To me blunders are the worst, they take you from good towards bad. So why do Blunders happen its only for one of three reasons 1) moving to quickly, 2) failing to analyse that situation, or 3) just not seeing something. So your blunders will largely be correctly by slowly looking at pobbile outcomes; not 3 moves in advance but even just one. You cannot help distraction or failing to see something but at least you can try.

So mistakes, these are not blunders but simply failures to move well; this is what i want to recognise since by avoiding blunders is what gets me to 1600 rating and avoiding mistakes gets me to 2000; we are all human and make errors but reducing my blunders and mistakes are the key to success in chess...