A stoppage-time header from substitute Simon Makienok earned the Lilywhites a 2-2 draw at the Amex Stadium.
They were playing with 10 men by then, midfielder John Welsh having limped out of the action after PNE had used all three permitted subs.
Last month at Brentford, they were in a similar boat when Marnick Vermijl went off with a hamstring strain.
Trailing 2-0 at the time, they crumbled to a 5-0 defeat.
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On Saturday, they were far more savvy, not allowing the home side to take advantage of having an extra man.
Jordan Hugill’s early goal had put them in front, before the Seagulls struck twice in 11 minutes in the second half.
Makienok’s leveller came in the second minute of time added on.
North End boss Grayson said: “We learned lessons from the Brentford game.
“This time we played with our heads rather than just with our hearts.
“Against Brighton, we stayed in the game, we gave ourselves an opportunity to get something out of the game despite having 10 men for the last few minutes.
“At 2-1 in a game, anything is capable of happening.
“Even at the end after we had made it 2-2, we got a free-kick in a good position.
“There was a chance to nick it then – it would have been daylight robbery had we scored but we would have taken it!
“I was pleased to see Simon Makienok get the equaliser because you want to see your strikers scoring.
“We have different types of players throughout the squad and Simon gives us something different up front.
“At 6ft 7in or whatever he is, his height is obviously going to give us opportunities.
“He has good technique too, as we saw when he scored the hat-trick at Bournemouth last month.
“When you have the wide players we have got to put in the delivery, Simon benefits.
“It was a great ball in from Paul Gallagher for the goal, you know that is what you are going to get from Gally.
“Gally has probably been a bit unlucky not to be in the team since he came back from injury but others have done well – I thought Ben Pearson and Daniel Johnson did well in midfield again, so did John Welsh before he went off.”
Grayson changed system during the game, starting with a 3-5-2 then switching to 4-5-1 for the second half.
“We were okay in the first half but I felt we were slightly vulnerable down the outside with the system we were playing because their full-backs bomb on all the time,” said Grayson.
“We changed to 4-5-1/4-3-3 to try and match Brighton up a bit more.
“That limited our attacking threat a bit, meant we could not take the game to them as much as we would have liked.
“But we had to do what we thought was best for the team.
“Unfortunately, Brighton showed good quality with the runners they have and their passing ability.
“For their two goals, that was something we didn’t deal with too well.
“After that, we didn’t let our heads drop and we kept asking questions of Brighton.
“It was just about working away and hoping that a break would come our way – it did and we took advantage to get the draw.”