Chess vs. Tennis - breaking through and momentum

The come-from-behind victory of Simona Halep in the 2018 French Open, which I just watched, reminded me of the Chess vs. Tennis lessons, as well as of course Andy Murray's breakthrough Grand Slam, after a huge amount of psychological pressure (both external and internal) to win.  The most important factor in Halep's victory was her being able to change the momentum of the game, which was all in her opponent's favor until partway into the second set (i.e. about halfway through the match).

Chessplayers experience very similar effects from momentum during an individual game, or over the course of a match.  The psychological impression of being under pressure, especially feeling that you are worse off and having to fight from an inferior position, can negatively effect your thinking and cause you to miss opportunities to equalize or even gain an advantage over your opponent.  On the other hand, it can also make us dig deep for strength and focus and lead to better play, eventually turning the tables on our opponent (as happened in Halep's match).

The best practical treatment of this phenomenon I've seen is in The Road to Chess Improvement by GM Alex Yermolinsky.  From the section on "Trend-Breaking Tools":

...Imagine a familiar scenario: your position is worse; moreover you feel that the trend is unfavourable.  You can't just sit around and wait, making normal, solid moves and watching your decline to continue - you may as well resign. This is what many chessplayers do - they mentally resign when things don't go their way.

Yermolinsky then goes on to offer several observations about how the momentum can shift, starting with a stubborn defence, assuming that the position is not in fact lost.  He says

...You may hate yourself for defending passively for many moves, but look at a bright side: your opponent knows he's better and he feels obliged to win - isn't that a pressure? ...Most of your opponents would be content with keeping their advantage in a secret hope that you'd go mad and self-destruct. If you simply can avoid that by just staying put, you'd be gaining some psychological edge even when your position is not improving.

He offers up a lot more besides this, but I'll let you see for yourself; the book is one of the best I've read on chess improvement.

Remember, if you can weather the storm and then start playing at the top of your own game, it can end with a victory...no matter the pressure.