If your "Plan A" for survival sinks, do you have a Plan B backup?
Forget rushing to the grocery store when disaster like a snowstorm strikes. Everyone else will have the same idea. Need I say more?
The supermarket and the convenience store are the first places a panicking town will flock to for food and water. While they're duking it out there, you can obtain essential supplies at other places where the masses of people won't even think to look.
Before some critical event hits, locate all the businesses and water sources within two miles of your home. When compiling this list, don't assume that any particular business can't possibly have something valuable. Once the list is complete, sift through it to determine if any have any valuable items. Take your time.
Businesses you might never think have water will have water, such as a dental clinic: bottled water. Same with beauty spas and health clubs. Many gyms also sell food. Don't blow off the hobby shop: It might sell craft wood and twine. And don't scratch off an office supply store: the big ones sell candy. Major bookstores sell bottled beverages, pastries and sandwiches.
Make sure you have a bicycle to get to these businesses in the event of a disaster, because a car won't be practical during or after an event like a tornado, hurricane or flood. And don't wait for the event to see if the bike works.
If you normally walk your dog or do fitness walks or runs, take different routes to get used to all the different routes throughout your town, in the event that a calamity obstructs your main route. You'll then instantly know an alternate route to get to a business to obtain essential supplies.
Finally, keep physically fit. Pedaling a bike for a few miles with a duffel bag full of food and bottled water will be very taxing for an out-of-shape person.