We don't need mirrors to see our own body right? We can look down and see how we look with our own eyes. It could be something like:
I looked down, fatigued and tired from my training. "heh" I chuckle to myself, "I guess the old man and his training is paying off after all" I observe as I notice my chest and arms are much more defined now.
It could be something along the same thoughts of:
He swings his sword at me and my body instantly knew what to do. My shield arm raises in defense easily blocking the attack. My arms are strong from years of harsh labor and training. My attacker was only able to realize this after the cloak fell off my body. He picked the wrong person to steal from. A lesson that he is about to learn the hard way. My thick powerful legs dig into the dirt, redirecting his blow with my shield. My right arm strikes the opening created on his left side knocking him to the floor in one effortless swing.
You don't need to sit there and do a look over in a mirror. A person can observe their appearance through other means whether by self observation (without mirrors or lakes) or through declaration of what the body has done. Forgive me for any issues with my samples. I made these up off the top of my head while I am on a break at work XD