Somthing like Remains of the Day which is about regret in life, or about friendship or about introspection. Things which do not induce doom or nihilistic feelings. I have read way too much stuff that induces existential crises like feelings and I end up craving the opposite as well, things which are full of life.
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In the short classics department, if you weren't handed them out when you were at high school, there's The Old Man And The Sea by Ernest Hemingway https://www.amazon.com/Old-Man-Sea-Ernest-Hemingway/dp/0684801221 . If you are considering emotional poetry, Des Imagists is short, historically significant and evocative https://en.wikipedia.org/wiki/Des_Imagistes
https://www.amazon.com/Old-Man-Sea-Ernest-Hemingway/dp/0684801221Hatchet (Gary Paulson) was a surprisingly emotional discovery tale of a stranded boy (Highly recommend it if you haven't read it). Green Book (Jill Paton Walsh) is a very heavily imagery-inspiring story of families leaving earth to survive on other planets in communities bringing very few possessions with them and figuring out how to survive.
And my own in-my-back-pocket recommendation for any occasion, Leonard Richardson's excellent Constellation Games: https://www.amazon.com/Constellation-Games-Leonard-Richardson/dp/1936460238
For the rationalist adjacent, I always recommend Crystal Society, the first of the Crystal trilogy by Max Harms (available online -- plus, three books for the 50 if you romp through them all!) http://crystalbooks.ai/
For short (novella) fiction, try All Systems Red, the first in the excellent (and light-hearted) Murderbot series https://www.marthawells.com/murderbot1.htm
Mono No Aware is an excellent, poignant scifi short story by Ken Liu. I've given it a few rereads now and it always brings me to tears. Online here: https://www.lightspeedmagazine.com/fiction/mono-no-aware/
For a very different (but also sad and beautiful) vibe: A River Runs Through It by Norman Maclean (the other stories published together with it are wouldn't call them emotional).
I loved Remains of the day, but for me even better was Never let me go, also by Ishiguro. It is borderline science fiction, which might appeal to you. It's very different and much shorter than Remains of the day. Some of the themes are similar, recollection of a past that brings reevaluation and new meaning to old memories. It's about and friendship and otherness. Ultimately though it's about acceptance of inescapable fate and finding joy in it, which seems relevant to what you are looking for.
I'm not really doing it justice, sorry.
If you have not read it yet, it's truly a masterpiece.
This got recommended to me on Twitter but "This is how you lose the time war" by Amal El-Mohtar and Max Gladstone. I'm surprise this hasn't already been recommended to you because it's been on everybody and their mom's reading list this year. Anyways, it's a super short read, you could probably finish it in less than 24 hours, but it's lovely, romantic, and certainly introspective.
There is No Antimemetics Division by qntm. It's got some cool sci-fi concepts, and is free to read online too. It starts pretty bleak but there's an undercurrent of love and hope which wins in the end.
https://scp-wiki.wikidot.com/antimemetics-division-hub
American Hippopotamus is a short (non-fiction) read: https://www.goodreads.com/en/book/show/19547849
The Book Thief is a historical fiction novel by the Australian author Markus Zusak, set in Nazi Germany during World War II.
The novel follows the adventures of a young girl, Liesel Meminger. Narrated by Death, the novel presents the lives and viewpoints of the many victims of the ongoing war. Themes throughout the story include death, literature, and love.
I don't know if this qualifies as 'not induce doom or nihilistic feelings', but it is about love and friendship and, for me, very emotional.