This is the part of a conversation between 2 people. I am trying to figure out the sentence structure of B's last reply.
A: I do that every day. That’s– [laughs] that’s really become– that’s really become a part of my– my practice regimen.
B: Oh, super! I’m glad that was useful.
A: Yeah, that was– that was extraordinarily useful. [laughs]
B: Yeah, it’s – it’s one of the things about playing guitar if you’re trying to achieve, yeah, higher than average level of technical mastery is that — you find that unless you’re like one of these freaky people who seem to be just super, super gifted, it takes an inordinate amount of practice.
In emboldened part "is that-", where is subject? I feel like there's some grammatical omission. If possible, could you show me the original version of last B's reply without any omission?