Failure to perform an accurate, reality-based risk assessment is one of the most common mistakes people make. Biases of all kinds get in the way, and lead people down a path of distraction, impracticality and obliviousness. Impulsive, bad decision making instead of thoughtful, methodical planning.
What is risk assessment? It's the process of identifying and prioritizing risks.
On a more concrete level, you step back and ask yourself a few questions:
What am I trying to do?
What could break/go wrong/interfere?
How severe would it be?
How likely is it to happen?
For an example, let's look at a fairly common activity -- commuting in your vehicle. Let's outline some common risks:
Motor vehicle accident
Dead battery
Run out of gas
Car jacking attempt
Flat tire
Vehicle immobilized due to conditions (bad weather, impassible road conditions)
Attacked by a mob of rioters or crazy bikers
Once we have our risks identified, we want to identify the big ones. Do that by triangulating the magnitude of the impact (will get you killed vs. inconvenience) and the likelihood of the risk occurring (common vs. very rare).
At that point, you have your risk assessment in hand.
Now, you can get to work on putting controls and plans into place to avoid or at least mitigate the effects of those risks should they occur. Your most severe / most probable risks should take precedence, but don't ignore the others.
These controls can take the form of activities or habits that you perform -- for example, always filling up your tank when you get below 1/2. Or they can take the form of physical preparations and gear--in the commuting example, that would mean carrying jumper cables, a jack and spare tire, gas can, trauma kit and so on.
A few other examples of some common activities, risks and controls:
Task: Family security and safety at home
Risks and controls:
Home invasion / armed robbery
Sturdy doors and locks, and the habit of always locking the doors
Alarm system (and habit of using it)
Dog
Home defense guns (accessible quickly, and training / mindset to use)
Family plan
Fire
Smoke alarm
Fire extinguisher
Family plan / evac routes
Homeowner's / renter's insurance
Off-site backups of important documents / data
Household accident
First aid kit and training
Emergency contact numbers
Family plan
Natural disaster
Designated safe room
Fire extinguisher
Comms gear (back up cell phone, weather radio, HAM radio if licensed)
Stored food and water
Family plan and evac practice
Bug out bags aka 72 hour kits and other survival supplies
Evac routes and destination planned
Task: Family security and safety outside the home
Armed attacker(s) (robbery, active shooter, kidnapping attempt, road rage, etc.)
Concealed carry license and handgun (carried regularly)
Firearms training
Self defense training
Anti-kidnapping / escape training for family
Trauma kit, flashlight, knife and other tools
Practice situational awareness
Avoid high threat areas and situations
Family plan
Vehicle accident
Trauma kit and training
Self-extraction tools within arms reach
Drive defensively and avoid driving in terrible conditions
Buy vehicles with good safety ratings / keep them in good condition
Natural disaster
Get home bags and supplies in vehicles and/or some basics in EDC gear
Situational awareness
Communications gear
Family plan, rendezvous points and evac plans
Task: Provide for family financially
Job Loss / loss of income (normal economy)
3 month emergency fund
Both spouses work (or are able to)
Maintain network of business contacts
Multiple income streams
Alternate skills
Unemployment insurance
Live within means and minimize debt
Food storage and other stores at home
Economic crash / banking system collapse
Cash on hand
Precious metal holdings / other 'tangible' investments
Food storage
Food production ability
Off-grid capabilities (power, water, etc.)
Ability to switch to 'barter' economy -- valued skills or production ability
Health problem / inability to work
Emergency fund and savings
Health insurance
Disability insurance
Both spouses work (or are able to)
Passive income streams
Live within means and minimize debt
You'll note that many of the "controls" are good for more than one risk -- those are smart ones to focus on.
You can get more specific or less specific than the risks above; focus on a very specific task or mission, for example. Here's another:
Task: Travel from home to bug out/evac location during time of emergency
Vehicle becomes stranded or stuck (congestion, road conditions, bad weather, EMP)
Travel in a group of 2+ vehicles
Drive 4x4s with off-road tires, winch and tow straps (less likely to get stuck)
Alternate routes planned (avoid getting stuck)
Maintain situational awareness
Alternate transportation (dirt bike and ATVs)
Have on-foot routes planned and packs for the journey
Bridge over river is impassible
Alternate routes planned (alternate bridge 15 miles away)
Plan to leave vehicles and float / swim across river
One vehicle to have inflatable raft in case of crossing
Attacked en route to location
Travel in group of 2+ vehicles
Take tactical driving course
Training and response plan (e.g., drive through at high speed if possible, else bail out from vehicles and engage)
Weapons and support gear in vehicles
On-foot routes planned / bags for the journey in case vehicles must be ditched or become inoperable
Communications gear to call for support
Trauma kits
Plan routes through decent areas, including alternate routes
Situational awareness
Avoid the temptation to focus purely on extreme impact events that have an extremely low likelihood of happening. Our minds have a tendency to focus on those big, scary things and artificially inflate their perceived likelihood of happening--that one in a billion event can become a perceived near certainty overnight. Devoting too much time and resources to any one extreme long shot event can be unbalancing, unhealthy and counterproductive.
There is also the idea of "risk acceptance," which is simply recognizing the risk exists but not taking any actions to control or mitigate that risk. You may choose not to take action because of cost, resources, laziness, acceptance of impact should the risk occur or your judgment on how likely the risk is to occur.
People do the risk acceptance math all the time, whether consciously or not. They live in hurricane zones but have zero in the way of emergency supplies, they say things like "if the crap hits the fan, I guess I will just die," or maybe they'd just rather spend their time and resources on fun and leisure. To each their own.
Corporate, government and military planning is full of risk assessment -- it's used by business execs planning expansion into new regions, NASA for planning missions into space, and spec ops units gearing up for a direct action raid against a terrorist cell.
Think through the eventualities, plan and prepare for the bad things that can happen.