I have started to play Chess again after a few years. It is not difficult to reproduce an opening or sticking with a plan during the middlegame, but the most difficult to me is to keep track of enemy pieces threats on open rows/diagonals/columns.
As an example during one game I've lost track of an open diagonal that has a bishop of the other player and no piece (white or black), and forget to take care of not letting pieces stay on that diagonal unprotected while I was thinking on something else (like a plan to stick with).
My question: Is there a tip or a known method of pros like "memorizing/imagine colors" or create a "mental X mark" inside all those squares that makes part of a enemy movement possibility?
Sometimes I get caught by those pieces that are full aggressive (not protecting anyone)...