Ianchus will be losing his strength, endurance, and stamina. All of his life, even if he hasn't had the most prowess in something, he's been able to push his body through it through sheer willpower and whatever strength he has. And now he won't have that, at a point where people will need his help, in all likelihood. He'll be upset, terrified that he won't be able to help people and will be useless (which pushes into his fear of being unneeded and unable to help).

He's also not used to being unable to tolerate pain. Another problem. Without giving his body to others, who is he?