Something that most persons not used to actual sparring ingore is that being actually hit on the face taxes your breathing resources too: most persons think there is no relation between being hit and breath (and i am not speaking of your ribs here), but there is.
ps you don't realize this connection immediately - when you realize there is (and you realize it clearly
then), it is invariably already too late, you're already treading on your knock down grounds.
At that point those who are new to that sensation try to conceal that their breathing
has been affected, and that's what leads to the actual knock down: they keep pretending they have not been heavily taxed, so that a few more punches finish them off easily.
Indeed, also relatively experienced fighters may try to conceal it because once you're there the fact is, you are taxed beyond rescue already.
You have lost.
Move here to minute 8.10: http://www.youtube.com/watch?v=yT9PQ2gOrnQ
get up, actually (in fact the left hook he threw at 8.05 was still vigorous
). The reason he decided not to get up is that he realized Hagler punches were taxing him - he could not breath
believe me... he decided that concealing
any longer was futile, he felt where he was heading.