There's actually quite a bit of emphasis and hints as to why the relationship with Elise, while perfectly workable as a real-world relationship had he moved forward with it, is failing Lehrgen in a certain kind of way and compensating for something instead of helping him be better. It's why he feels the blow so keenly, because he doesn't have the crutch anymore, but as to whether that support *should* have been a keystone to his life is a bit of a different story.
Elise is/was, I guess, more of a typical relationship - as he mentions in this very chapter, he felt like she went out where he went in or something along those lines, and their puzzle pieces just kinda fit together instead of taking it upon himself to make his piece have fewer parts carved out of it. Getting to our other thread, it's kind of how I see Tanya & Visha. A very common approach in real life to take to a relationship; harder to make a really compelling story out of in a way that feels truly romantic, especially if the end goal isn't just the relationship but getting Tanya to actually have to try a different approach than her CSE-approved one.