When you analyse your plays in a negative light you pick out all the mistakes you made, as opposed to many trying to find a way to pit the blame on someone else.
It is very easy to mislabel things and end up locking certain plays mentally. this ends up causing more problems, you need to be flexible in league.
EG you failed to kill in a 1v1 but also didn't die: See's jungler doing blue and thinks "he shoulda assumed I would go in, stopped doing blue and ran up to help secure it, thus it's his fault he got away" Not that the player may have missed spells, miss clicked and AA'd a minion, overestimated his damage or didn't take enemy summoners into account.
Watching that over again won't help this player, they had plenty of very clear mistakes made in a row that led to that falure, if they can't catch it on the first runthrough or on the grayscreen, they aren't going to catch it.
There is far more to gain from critically analysing your mistakes than analysing the "shit dogs" so you can find a way to place the loss on them.
I am not saying that this is untrue.
When I started doing it I shot up from bronze to less bronze (silver). A small hop but a hop that required improvement in some regard. And I couldn't improve if I didn't acknowledge what I was doing wrong.
If something so small was holding you back, then odds are it was your psyche and not your gameplay. such has occured to too many people I know.
So instead of sugar coating it and going "it wasn't that bad" it was "you missed this piss easy point blank skillshot, auto attacked a minion then cancelled 3 autos due to constantly switching between clicking on the enemy champ and minions. The enemy then flashed away, I flash under them but forget about the tower that is now shooting me during all the commotion and I die".
You will end up locking yourself into around gold or low plat with this, maybe higher if you can hold absolute mastery a few champions, but you won't be noteworthy otherwise, because you will lose flexibility. If you focus on never making this mistake again, you will lose a tool, a choice that can be made.
Instead of doing that, you should think "I should have done this another way" and then visualize how exactly you could've succeeded, both in the same situation or with the same play.
I don't think people understand me really. Critisizing ones mistakes is not my problem here, but specifically focusing on the negative of it is.