During his first inaugural address, Franklin Delano Roosevelt said, "the only thing we have to fear is fear itself...". While it's a great sentiment, it's not entirely true. Not all monsters are make believe. Nature and the world can be a pretty scary place and a little healthy fear can keep you alive.

Reddit user SkeletronDOTA asked people "What is the scariest, most terrifying thing that actually exists?"

Here are the frighteningly real answers.

The fact that anyone at any point could just drop dead from a brain aneurysm.

I have had Carbon Monoxide (CO) poisoning 4 times in my life. I feel like I'm cursed. I have 3 CO detectors in my house now and a way to quickly flood the house with fresh air if needed. 2 years ago we got a new wall heater because the old one started to spew out CO. Something went wrong with the new heater and within 2 weeks of installing it we almost died from CO. Right now just typing this I started to feel woozy and had a mini panic attack that I was suffering from CO poisoning.

Large rocks minding their own business in space that might run into our planet and end everything someday.

People that kill without a conscience or reason. You could be in the wrong place at the wrong time or even just asleep in your home, and someone could pick you for no reason at all other than opportunity.

This plant: Dendrocnide moroides.

Also known as the stinging brush, mulberry-leaved stinger, gympie gympie, gympie, gympie stinger, stinger, the suicide plant, or moonlighter, is common to rainforest areas in the north east of Australia. It is best known for stinging hairs that cover the whole plant and deliver a potent neurotoxin when touched. It is the most toxic of the Australian species of stinging trees. The fruit is edible if the stinging hairs that cover it are removed.

Sudden random ballistic missile alerts at 8:07 on a Saturday morning while you're tidying the kitchen.

Methamphetamine addiction. I worked with children who didn't understand why they couldn't see their parents anymore and hearing an eight year old tell me they just wanted to go home was heart breaking.

Amyotrophic lateral sclerosis,

At least with Alzheimer's the patient usually doesn't really know what's going on. With ALS, the patient has minimal mental impairment and is trapped in a non functioning body.

My cousin's wife suffered from and passed due to ALS. I wouldn't wish it on my worst enemy.

Cordyceps: Lethal mind control fungus.

It only infects insects (as far as we know) but it's straight out of a horror movie. Infected ants compulsively climb as high as they can and then clamp their jaws down. Then a stalk grows out the top of their head and releases spores that infect more ants.

"Honey, sit down. We need to talk." Nothing good comes after that. Nothing.

Hippopotamus. They can weigh about two tons and achieve speeds of 20mph on land. Their bite can easily kill and they are extremely territorial. More deaths occur per year by hippos than lions, bears, elephants, and sharks combined.

Rabies. Don't google videos of people with rabies.

There is no cure for advanced rabies. There is a vaccination, but if you don't get it in time or at all and it travels to your brain, which can take a few days, you WILL die. So if you get bitten by a strange animal scrub the wound thoroughly and INSIST on a rabies shot.

The trust in others that everyone has everyday when they drive. While driving from point a to b, every car you pass, or that passes you could easily kill you with a wrong turn of the wheel or loss of control (especially when it's something the driver can't help, like a seizure).

"Bleeding eye fever"

The symptoms of the viral disease are said to include headaches, bleeding, vomiting, diarrhea and muscle pains. The viral hemorrhagic fever is said to leave people bleeding from their eyes, mouth and anus. Other symptoms include dizziness, body stiffness, backache, sore eyes, abdominal pain, mood swings and confusion.

The fact that you can be paralyzed and unable to move any part of the body while your mind remains completely intact.

Anesthesia awareness - You go into the hospital for surgery and you are paralyzed and awake during the entire procedure. unable to scream, move, or indicate in any way that you are "locked in"

The fact that I am allowed to structurally weld bridges which hold thousands of cars a day.

Granted none of my welds have failed a test and I put forth my best effort every time. But still, if one decides to fail. .. Yea that's a scary concept.

Take a look at 5 of the world's most dangerous chemicals - video. If they were anywhere near as common as animals with rabies, any one of them would be a clear winner.

Drifting away from a space station with no way to get back.

Couples or any "pair" of people who commit hideous crimes together. How much trust must you have in someone to confide this desire. " Hey Jane, what do you say we abduct and kill a stranger today?" "Oh sure Richard, it will be our little secret."

The idea that the sickos can find each other like this scares the living sh!# out of me.

Being attacked by a great white seems pretty terrifying. I was paddling around on a skim board for scientific purposes one time and saw a large dark shape pass under me from left to right. I literally screamed like I was in a horror movie. Turned out to be a sharkly shaped section of reef that the current was carrying me over. At the moment though, it was still top 3 for scariest moments of my life.