Don’t Starve – How to Restore Sanity While Playing as Maxwell

You can find all the informations you need on the wiki.

Basically at the start of the game you're given a treshold of 30 Naughtyness. Every action damaging a "nice" creature subtracts points from this treshold according to the following table:

When you reach 0, one or more Krampii (Krampuses?) will spawn, depending on the days you've survived:

Every 60 seconds spent not doing naughty actions will increase your threshold by one, so this means that if you try to space out your killings in time, you can safely keep hunting for your meat without fearing to meet Krampus. On the table above the "Treshold" column indicates the maximum naughtiness you can have. It has been put in there because it's supposed to go down the more days you play, but there's still an uncertainty on the exact numbers, hence the interval.

The fastest way to reduce your sanity reliably is to eat Green Mushrooms, if you have them available. They can be found in Forests and the Savannah, can only be picked at Dusk and reduce your Sanity by 50 points, with no HP loss. With 1-2 raw Monster Meat pieces on top of that you'll become Insane in no time, just remember that Monster meat deals damage when eaten.

The only thing that gets close to that amount of Sanity loss is a Grue(a.k.a. the Night Monster) attack, that reduces your sanity by 20, but that is risky, since a couple of hit in short succession can easily kill you.

When you're done harvesting your Nightmare fuel, you can quickly gain Sanity by sleeping in a Tent: at a whooping 50 Sanity gained per use it will easily soothe your shaken nerves letting you finally get some good nights of sleep after facing your Nightmares. If you're having problems getting the Spider Silk required by tents, you can always create Straw Rolls, that let you get 33 Sanity per use.

Happy hunting!