Yeah the rejoinings at first were probably easy for Emet to deal with and swallow. But the closer the sundered came to looking like an unsundered. At least soul wise I'm sure it became a harder thing to do. He really does want out of his burden, but has struggled to find a way he be "fine" with. He wants to both be proven right that we're unworthy of being handed the baton and that the WoL really isn't as good as their past self. While also wanting to be proven wrong.

He is a grief stricken lonely man who feels as though it's all up to him to see the rejoinings through since Lahabreha went mad and was killed. Then there's Elidibus who chose to slowly lose his memories until he's no more than just a body that's a slave in a way to his duty. Emet by the time we meet him is so done with the rejoinings and wishes they could be sped up. That he could stop being asked to build up nations just to know that they'll be destroyed. With probably a bit of bitterness lingering about a few things. It's why he looks like he's enjoying spending time with us and teaching us stuff. Only to have an emotional outburst and get back into the kill you all mind set. You see it happen with Elidibus as well but that's more of getting mad at not being able to remember and then getting mad at just wanting to remember.