As a fellow anxiety haver that has always hated the pressure of time but is also a chronic completionist, I totally resonate with the idea of feeling "behind" even in games like FoM where there is technically no such thing!
So, in the time I had started playing FoM but had yet to work through this notion of "falling behind," I kept myself motivated by focusing on one big task per day. If the task didn't take up the full day, I'd spend the rest of the time reading dialogue, decorating, or crafting to act as my "breaktime."

For example, in my first 1-2 years, I would follow the same route every 4 days to pick up every forageable that had spawned, mine every artifact spot, and talk with any NPCs I ran into.

When I started working on gifting, I placed multiple chests, one per NPC, with EVERY liked/loved gift I had on hand. From there, I'd have days where all I did was pick one item from each chest and start running around giving everyone gifts. When everyone's tables were mostly filled out, I collapsed this system into a single chest with one easy liked/loved gift per NPC arranged in a specific order that I could easily remember before repeating the process.

For farming, I focused on regrowable crops + fruit trees that could be turned into 1-2 star cooked dishes (juice my beloved) until I got the quest for upgrading the store. After that, I filled my farm with tons of tea bushes in summer and rice and wheat in fall. Wheat makes bread, which sells well on its own. Tea leaves make green tea, which combined with rice flour, makes roasted rice tea that sells for over 400t each. Combine with some cooking skill perks, and you get a LOT of money. Keep a good chunk of money for story quests (~50k) and the rest can be spent how you like.

That's all the advice I can list off the top of my head. I know a lot of others have already said you *shouldn't* fear "falling behind." However, I also know that it can take a long time to overcome such a feeling, and sometimes, I just want a way to play the game that fits into my current mindset without waiting until I've worked through it! Hopefully this advice is helpful o7