Many writers keep a diary or journal, even if they don't write in it consistently. I try to update my journal at least once a week, but sometimes, I only write in it when I'm having a horrible day and I need something to vent to that's not going to judge me or gasp at my choice of bad language. When I have time, I read my old journals and am often surprised by things I had forgotten about or by how much I've changed over the years.
Recently, a friend of mine said she was feeling unmotivated and uninspired to write, so I encouraged her to journal. What she wrote wasn't important, just the fact that she wrote. She could ramble and go off on tangents and not make any sense at all--it's her journal and no one has to see it.
I've found notes for story or novel ideas in mine; life goals I set for myself; resolutions; and a whole lot of rambling nonsense that must have made sense at the time. I love being able to express myself with no reservations in my journals. I write a lot of things in them I wouldn't say out loud. Just writing it down really helps. It's like having a personal therapist, except you don't have to pay by the hour and your appointment is anytime you feel like it. Instead of a therapist offering insights into your personality, however, you have to discover those insights yourself.
If you've kept journals for a long time, go back and read your early ones. You might not only find some ideas and inspiration, you might also find out some things about yourself you didn't know.