Letting your cat run loose outdoors and catch diseases from mice, other cats, getting hit by cars, eating a mouse that's eaten mouse poison, and more. Keep your cat inside. Feed it properly, give it a bath at least once a year, brushe it weekly, and give it lots of love. A cat that's well cared for and kept inside can live to be 15-20 years old.
Had 2 cats that lived to be almost 17. They were both indoor cats. My sister lets all but one of her cats go outside all of the time. The outdoor ones have rarely made it to age 10.