"Flip-Coin Chess: Does not pay attention to all (or sometimes even any!)
of the threats generated by the opponent's previous move.
Hope Chess: Does pay attention to all the threats generated by the
opponent's previous move, but, before making their current move, does
not check to make sure that all checks, captures, and threats by the
opponent on the next move (in reply to that move) can be safely met.
Real Chess: Not only deals with opponent's threats from the previous
move but, before making their move, also makes sure that the opponent
will not have any checks, captures, or threats that cannot be met after
that move, and does this check on every move possible/necessary."
[...]
"One key to promoting yourself from Hope Chess to Real Chess is checking
for upcoming danger *on every move, and not just most of the time*."

— Dan HEISMAN

Chess Quotes

"In order to improve your game, you must study the endgame before everything else, for whereas the the endings can be studied and mastered by themselves, the middle game and the opening must be studied in relation to the endgame."
— Jose Raul Capablanca, World Champion 1921-1927

  [More endgame quotes?]