"Hah. No, I was—the bull thing, that was a joke. I'm no bodybuilder, and I appreciate your pointing out that I was biting off more than I could chew. So to speak."
Other options:
Re: Day 2
"Hah. No, I was—the bull thing, that was a joke. I'm no bodybuilder, and I appreciate your pointing out that I was biting off more than I could chew. So to speak."