I see a lot of complaints about the Plains, specifically deathsquitos. I used to agree that they were too difficult. Deathsquitos, fulings, and loxes all needed to be nerfed. I no longer think that. Here's the thing about entering any biome for the first time, beat the one that comes before it. Don't explore the Swamp until you've mastered the Black Forest and don't explore the Plains until you've mastered the mountains. If you have, then you know how to shoot drakes out of the sky survive a pack of wolves, and you can defeat a stone golem. That will prepare you for deathsquitos and fulings.
If you know, or even suspect, you are getting close to the Plains, start sneaking. Don't just stroll or worse, run into the biome and then wonder why you were killed so quickly by a deathsquito. I've gotten very close to one and lived to tell the tale because I was sneaking. I also used a bow to clear all the deathsquitos in an area. Then I sniped all the fulings, then I hunted lox. If you take these enemies one at a time, be patient, use your meads, and keep your shield up, I promise it will be quite easy to not die.
Be aware of your surroundings, eat the best food available, and take your time. Don't be afraid of your enemies, but understand their strengths and neutralize them. Take advantage of their weaknesses and they will fall before you!
One more thing, if you are exploring a new area in a boat, watch out for land and keep your distance. The trees will tell you which biome it is. The color of the sky changes as well. Turn the sound up and you will hear enemies coming. Look at the map and draw an imaginary circle around the original spawn circle. Plains only appear when you are far from the center of your world. If you are in the Plains zone, you should be ready for a deathsquito to come at any time. Tack back and forth and clear the fog of war. Mark known Plains on your map and don't get close until you are confident in your abilities to protect yourself. Find Black Forest biomes to explore on foot. Follow the shore to map out the shape of your new island. Then you'll be able to find a safe route to sail. Remember some Plains biomes are just tiny islands that can still spawn deathsquitos! Also, drakes can fly out over the ocean.
TLDR; plan ahead and prepare before you set foot in the Plains and you'll survive.