If you're over 45, get a colonoscopy.
I know someone in her 60s who recently had her first colonoscopy. They found a tumor, requiring surgery to remove a section of her colon. She had no symptoms before, and is an otherwise healthy and active person.
The pathology report showed that the tumor had just penetrated the outer wall of her colon. If she'd waited longer, it would have metastasized. An earlier colonoscopy could have nipped it as a polyp.
Just do it. It could save your life.