Picking flowers is +5 sanity (usually the simplest fix), prototyping something is +15, sleeping in a straw or fur roll is +33 (at the expense of -75 hunger), sleeping in a tent or lean-to is +50 (also -75 hunger). You can eat a cooked green cap for +15 (and -1 health), or just about anything out of a crock pot for +5. Eating jerky is +15 and small jerky is +10.
If you’re playing as the robot, gears are +50. If you’re playing as Willow, standing really close to fire will increase your sanity.
Of all of those, the simplest are picking flowers and eating cooked green caps. Collect 12 flowers and make a Garland which restores 1.33 sanity/min while worn. “Dapper” clothing items like the Top Hat will restore 3+ sanity/min.
Just pick flowers whenever you come across them and you’ll be okay. Eating the petals also restores +1 health, or you can just drop them and they’ll become rot which you can use as fertilizer.
Be careful of things that quickly reduce your sanity, like digging graves, picking evil flowers, or eating spoiled foods, any raw meat, durian, and never ever eat monster meat, monster lasagna, or blue caps.
Also, build a Bee Box. Place it in a forest, grassland, or savannah biome a couple of screens away from your base (you don’t want it too close or you’ll have bees buzzing around all the time) and it will create lots of flowers which you can then pick to keep your sanity up.
Okay, last night I was able to get to day 21 before dying from insanity. I did this by making and wearing a garland, and never eating anything uncooked. If it can be eaten, I cook it, even seeds. I found that if I eat any uncooked foods, with the exception of berries, my sanity decreases.
Also, and I am not sure about this, it seems if I keep my belly full my drop in sanity slows. Again, I am not sure so I will have to continue to test it.
The problem with the garland is the increase in sanity is so small that if my sanity is decreasing all it does is slow the decline; it doesn’t reverse it. Another problem with the garland is that it wears out over time, and you need 12 flowers to make one, so if you have picked all the flowers on your islands, you’re out of luck until they grow back.
One good thing is I was finally able to live long enough to build a science machine. There is something I need limestone for (I don’t remember what at the moment) but where can I find it?
You can also make a flower hat which typically restores enough sanity over time to counter natural drop and the occasional rain shower.
The most important sanity drops should be avoided however : sticking too close to monsters (don’t fight spiders, trap them instead. Keep the fuck away from Treants, swamps, etc…) and letting light drop down too far. Lighting your nights with a torch (or worse, a lighter) is not enough, and if you build a fire or firepit you can’t just feed it efficient scraps and let it live at the minimum level of light - you need a real blaze going.