Any teacher worth their salt – it doesn’t matter if the subject matter is yoga or biology – will be learning from their students as well as teaching them. That’s how teaching becomes an art, and it’s what makes teaching a great profession.
One of the things I had to learn about some students is that they either cannot, or have a great deal of trouble, distinguishing between discomfort and pain.
I believe most pain, especially when it is acute and extremely intense is to be avoided. However, discomfort may just be related to experiencing something unfamiliar, like stretching hamstrings when they have been allowed to tighten up over longtime. In this case, tolerating the discomfort of stretching those hamstrings will pay off if one exercises regularly and conscientiously.
I’ve worked with students who at first, when they experience discomfort, are very reactive, coming out of a pose immediately or holding their breath. When they learn to tolerate it,  discomfort gradually diminishes. It’s something about stopping resistance, and also just becoming more familiar with one’s body and not so fearful.
Another spin on pain comes from the yoga sage, Patanjali, in The Sutra 2:16:

2.16 Because the worldly experiences are seen as painful, it is the pain, which is yet to come that is to be avoided and discarded. (Heyam duhkham anagatam.)

What does he mean? The sensitivity that we can develop through our yoga practice will help us avoid mental, emotional, physical, perhaps even spiritual difficulties of the future.
The words and deeds you do today will shape your future character.
The exercise and diet of today will create tomorrow’s physique.
I’ve been carefully noticing how easy it’s been to let slide my good diet habits over this month or so of socialising in favour of more eating and drinking. One of the “discomforts” I’ve experienced is difficulty in waking up in the morning. So, Patanjali’s advice hit home with me today, and tomorrow should be a more abstemious day.