I believe there are a few Lemmy instances that don’t have downvotes enabled. (Beehaw might be one of them, but don’t quote me on that.) If downvotes are a stress point for you, you could try joining one of those instances.
I personally find both upvotes and downvotes to be useful as a way for me to quickly see the community’s reaction to a piece of content. If I’m scrolling through my feed and see a post with many downvotes and few upvotes, for example, I know that post is unlikely to interest me and will move on. Conversely, a highly upvoted post or one with a mix of both upvotes and downvotes is more likely to have a good conversation in the comments in my experience.
If I make a post that receives a large number of downvotes - or if most of my posts tend to be downvoted - that’s a signal to me that I’m either not communicating my message well (confusing, passive aggressive, etc.) or that my message itself may not be welcome (hate speech, misinformation, etc.). In either case, I use that as a mental trigger for me to reflect on my posts rather than a reason to become unhappy with the community/platform as a whole.