Past a certain level if you want to play for a win you have to play sharp openings. You wouldn't be losing objectively, just have far fewer options than other kinds of systems.
To play great chess, should you always be hovering at the edge of defeat?
I think this just means;
Reaching for safety will mean that you miss things that were less safe, but better.
There is always a balance between things in everything, a pay off for an advantage, and sometimes you can try to avoid paying anything and end up with nothing.
However, don't take this too literally and start putting yourself near defeat because you think it will lead to victory.
There is no magnitude to victory, you either win or lose, so don't try to win too hard, just winning is enough.

It's easy to see the beauty behind sharp moves. I mean, any rookie (including me) can see how shocking are some sacrifices, even if he doesn't understand why that move was made. And we all agree that sacrifices are cool.
But in order to understand quiet/positional/prophylatic/defensive moves one must be very precise and cold-blooded. Do you know the expression "speculative defense"? Surely not, because it doesn't exist.It's easier to attack than to defend.
"What I value more than anything in chess is logic. I am firmly convinced that in chess there is nothing accidental. This is my credo. I believe only in logical, "correct" play."
Tigran Petrosian

That's more Hollywood drama and less practical for a tournament player. Being on the verge of losing implies taking unwise risks and taking the game to very murky levels of uncertainty in order to provoke a mistake from the other player.
That can work in blitz and also works if you are already losing. Pretty stupid if you in a slow + serious game and idiotic if you are ahead.
Everyone's not Tal. We're more likely a##hats with delusions of grandeur.
I think the point about playing the man vs. the board is:
There's honing skills + acquiring knowledge and then there's tie-break criterion that could matter under very specific circumstances.
For mere mortals, spending time and energy on the former is expected; gamesmanship + psychology is more of the latter and is best left to the professionals or people hustling in the park :)
I saw part of the movie Searching For Bobby Fischer the other day, flicking through channels. It showed an actor (Lawrence Fishbourne), playing the part of a local chess hero at a park, coaching a boy in blitz, and as the boy was moving faster, he was spurring him on, and Fishbourne said something to the effect that to play well you have to be always on the verge of losing. How much merit is there in that? Is that the way most masters play?
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Vinnie: He didn't teach you how to win, he taught you how not to lose. That's nothing to be proud of. You're playing not to lose, Josh. You've got to risk losing. You've got to risk everything. You've got to go to the edge of defeat. That's where you want to be, boy - on the edge of defeat.
Josh Waitzkin: But...
Vinnie: But what? Play. Never play the board, always the man. You've gotta play the man *playing* the board. Play *me*. I'm your opponent, you have to beat *me*. Not the board, beat *me*.