If you're going to be a writer, the first you need to be is creative.
And being creative means you need to be receptive to channeling new ideas. Your mind is like a cauldron, where you stir in a bit of this and a dash of that (eye of newt, perhaps) and they spark together to form something worth pursuing.
Ideas (even great ones) fall on everyone. But if that's the case, why aren't more people richer and more successful? Because most find themselves tossing the ideas away as silly and risky for their way of life. It's safer just to go through life, not rocking the boat, and drifting through an existence. Pursuing a fresh idea would be challenging, and could be dangerous to those around you who just want you to "get a job and be like everyone else."
It's risky to pursue your dreams, and boldly put yourself out there, working hard to make a difference. Is it easy? No way. Is it worth it? Yes!
I carry a notebok around with me most places, and for times when I don't I use the "note" feature on my cell phone. Ideas can come to you at any time.
Ideas are like rain. Rain falls on everyone. Most people, however, just put their umbrella up and let the ideas bounce off and fall into the gutter. I'll bet that the idea for Microsoft and Apple hit dozens upon dozens of others before Bill Gates and Steve Jobs (and Woz, can't forget him) took up the mantle and risked their ideas on humankind.
I challenge you to walk through life with an upside-down umbrella, capturing as many ideas as possible. You may use only a small percentage of them, and that's okay. After a while, you'll start to recognize the good ideas from the bad, and even a few of your good ideas will become great. Because even Harry Potter and Star Wars started out as an idea.