Have backups - for EVERYTHING. And have backups for your backups.
Have at least 2 of everything that's really critical. Always buy more hay/feed than you think you'll need for a given time span. Have at least two fully stocked first aid kits (one for you, one for your horse, but know that you can always use your horse's first aid kit for yourself in a pinch ;p ). Have photocopies of your horse's records, ID, your own ID, etc - one in your tack box, one in your car/truck/trailer. Have an extra phone charger in your tack box, and one in your car (cell phone batteries always run low at the worst times). Have emergency plans for any sort of natural disaster or personal disaster, and have a backup plan in case that one fails. Have a backup bank account you keep a minimum of $500 in for emergencies.
Basically, if it can break, get lost, get stolen, or fail - have a backup for it.
I also keep what I lovingly call my "Zombie Apocalypse Kit" in my car, and my spare kit in the barn. These kits have saved my butt more times than I can count. Here's what's in them:
- 1-2 person "quick up" tent
- Sleeping bag rated to 0 degrees (in the barn), rated to 20 degrees (for in the car)
- an inflatable pillow
- A crank lantern
- A basic tool kit
- Extra bottles of water
- Non-perishable foods (I usually buy self-heating MRE's)
- Extra outerwear (jacket and/or sweatshirt)
- Extra clothes - EVERYTHING - underwear, socks, sweat pants, etc.
- A hat
- Extra shoes
- A favorite book
- Toiletries (TP, Advil, travel toothbrush, etc).