Goals from Pierre-Emerick Aubameyang, Mario Gotze and Raphael Guerreiro – combined with an own goal from Benjamin Stambouli – had put Bosz's side well in control by the 25th minute of Saturday's Bundesliga encounter at Signal Iduna Park.
But two goals in the space of four minutes hauled Schalke back into proceedings after the break, before Aubameyang's dismissal for a second bookable offence put Dortmund on the back foot.
And Schalke's numerical advantage eventually proved too much as Daniel Caligiuri cut the deficit to one and Naldo headed home an equaliser in stoppage time to cast further doubt over Bosz's future, with Dortmund now winless in their last six games across all competitions.
"We will have to work hard, I did that all my life," said Bosz, who last oversaw a top-flight win in September.
"That's the kind of player I was, I never gave up, and as a coach I will not give up either.
"I will cheer up the players, nobody needs to cheer me up, I'll do that myself. I did that all my life and I will do the same now.
"It was a crazy game. If you were there, you cannot believe it, that is, I cannot believe it."
2 - @s04_en is the 2nd team in the history of the #Bundesliga to come back from a 0-4 deficit after Bayern Munich in 1976 (6-5 win after 0-4). Mindset. @s04_us #BVBS04 — OptaFranz (@OptaFranz) November 25, 2017
Bosz offered no excuses for his side's dismal defending in the second half.
"We started well and if you are leading 4-0 at half-time you can never draw 4-4," added the Dutchman.
"I believe that happened because in the second half we didn't play clear football. The first half we tried to play football, we did it very well.
"We didn't take advantage and when you look at the way we conceded the goals, that just can't happen on our level. Unfortunately it did happen."