Secrets of the Past

The sun shines outside, But I live in the night. No one knows what I hide, I keep it hid out of sight. Secrets of the past, Darken even the brightest day. They're there to last, Shadowing every ray. Sometimes they try to flow out, But not for long. I am to stout, I have become to strong. Keeping it all in, Has become an easier fight. So far I always win, Keeping it bottled up tight. If it comes out, I may not last. I would have to scream and shout, And it could destroy me fast.