urge itch

Hi, I am doing my work on urges, but more in general to allow both emotions and sensations. I am wondering if our brain is confronted with an intense sensation, like a burn in our legs because we are maintaining a posture in an intense workout, or like a challenging yoga posture. We want to stay there and allow the sensation and breathe through it. Indeed I recognize that I can find ease with it and “be more comfortable with the discomfort”. However, I obviously cannot allow the sensation forever, at a certain point I just cannot hold the posture any more. Similarly, I can imagine myself with an itching sensation. I see I can allow it as long as it is manageable, but I also see that at some point my brain will freak out, just as a neurological response to the sensation. So my question is can we really always allow both emotions and sensations? Or to what extent can we really do this, or when it gets unrealistic. I am sure I can allow the urge to leave the yoga posture or allow the itching but only up to a certain level of discomfort. I think clarifying my mind on this can help me also with managing my urges to buffer. Thanks