You are full of your material—your family, your friends, your region of the country, your generation—when it is fresh and seems urgently worth communicating to readers. No amount of learned skills can substitute for the feeling of having a lot to say, of bringing news. Memories, impressions, and emotions from your first 20 years on earth are most writers’ main material; little that comes afterward is quite so rich and resonant. By the age of 40, you have probably mined the purest veins of this precious lode; after that, continued creativity is a matter of sifting the leavings.
This is every true. Many authors are full of material, it's just a matter of writing it. I find myself filled with so many storylines I don't even know which one to begin with. I even find myself writing 3 projects at once. Sometimes the things that happen to us in our lives do make a good story. It's just a matter of writing it into something people can relate to.