Besides being a really clever interpretation of the theme, this game presents a perspective on mental health that feels under-represented in games. I love Yume Nikki, and there are a lot of games like it that stand as visceral, impressionistic portraits of depression. There's a lot of value in these (both for people who relate and for people who otherwise might not be able to) but off the top of my head I can only think of a handful of games about getting better something The Mouldering Form doesn't help with so kudos for that.
In terms of design, I think 2-3 more repeatable sources of mental energy would really make this sing. Mechanically, this mostly just makes the waiting periods where you're otherwise just spamming the computer more interesting. And to be clear, I love the computer and the little messages! But speaking as someone for whom online friendships were life-saving, my mental health got a lot better once that was no longer my only source of support, and conversely, as my mental health got better, I found myself able to practice a wider variety of self-care. Which is to say: I think it would support the narrative as well if you're interested in expanding this after the jam.
It's rare for a jam game to hit this hard as a work of art for me. You should be proud!