Looking over games where you blundered+ Visualization question

I find it hard to make myself review games where I lost due to dumb mistakes. This is because I just tell myself that had I not made that one move, I would have won, and therefore there's nothing to review. I want to know if others have similar problems.

Also, I heard from IM Rensch that knowing the color, brother square, and diagonal of each square will dramatically improve your chess via better visualization, board vision, and less blundering. Is this a myth or is there truth to this statement?

You're right about the bumb mistakes.  I used to review a lot of my games but the winning or losing of each game can be, more or less, decided by who makes the most blunders (at my level).  I decided just to try to eradicate these big errors I regularly make, to no avail as yet.  I was interested in your comments from IM Rensch,and I intend to rty it.  Just need to understand what he means by 'diagonal' (I understand that the 'Brother Square' is the same square from your opponent's viewpoint).  Could you enlighten me on the diagonal?

but was it visualisation, how does Rensch visualise anyway. I mean i can calculate some moves deep and it goes. But i cant visualise the end position, i mean i know what postion i reach and what it looks like but i cant visualise it alone

You're right, of course, Paul.  But I've analysed them and usually it's just that I missed an obvious move (by him or me).  I can easily see what I've done, but I'm darned if I know why.  I usually see it immediately I press 'submit',and I've put thought into that.  Why can I look at the board for a good few minutes and miss a move that I then see in an instant!  Maybe at your level the blunders are more subtle, but not with me.