You see many shows on National Geographic, etc, showing preppers who take things to the extreme... Storing away years worth of food, stockpiling guns and ammo, building deep bunkers and faraday cages... These people are preparing for extreme solar flares, chemical warfare, nuclear fallout, supervolcano eruptions... All manner of very nasty things. Nasty, yes, but unlikely to happen.
My personal approach to prepping is the realism of it all. What is ACTUALLY likely to happen? Sure, there are things going on in the world such as the nonsense with North Korea, international terrorism and near-earth collisions with meteorites, but all of that, in a real sense, has a small likelihood of affecting you, and the odds of you being able to suitably prepare for it are slim.
So what could REALLY happen? Well, one thing that has been proven, empirically, lately, is the effect of carbon dioxide emissions from humans over the past several thousand years.
You may have noticed that in the past several years, the number and ferocity of natural disasters has been steadily increasing... Well, just recently, papers were published showing hard evidence of why this is happening. The reason comes down to carbon dioxide in the atmosphere, which has recently hit a record high (during human occupation of the planet) of 400 ppm.
As soon as it hit 400 ppm the Earth itself started to go into a "cleanse" routine. It's not the first time it's happened, either. Before people evolved into what we are, the Earth built up its CO2 levels through excessive volcanic activity, leading to large amounts of gas releases and forest fires caused by lava, which blackened the atmosphere leading the planet to generate huge floods and tornadoes, etc, to, essentially, hit the reset button. Now it's happening again.
A good read of the proper data behind these findings can be found here. If you'd like a simpler, quicker version, check out this slightly sarcastic video by noted ex-physicist Henry Reich:
So, this is something to think about when justifying your prepping. It's not some crackpot, spurious thing. It's real, and it's already happening. Australia has been having massive floods and cyclones, North America has endured relentless tornadoes and Asia has had to slog through giant earthquakes and tidal waves... It's not coincidence, and all of the evidence points to the fact that it's just going to get worse.
So be prepared, stay safe and keep informed.
P.S. Here are some reference links to back up what I've been saying: