I think its most important to push the mental limits...less danger there, and often more benefit. The physical limit pushing is important when you are basically healthy and in shape. After a layoff, especially, I would be cautious about how and when I push against feeling physically ill (I'm over 40, so there are legitimate health concerns). I would expect someone in their 20s to have different limits, of course.
I think the marines (or some military group) ask the question 'are you hurt or are you injured?' You push through being hurt, but when injured, assess the injury before further training so that you don't damage yourself. Its often not as clear when it comes to coming back on the mat after a layoff...
For what its worth,