I had a great idea about something the other day. But I didn’t write it down, so now I have no idea what it was. Let that be a lesson to you. Inspiration is a fickle bitch. The best and probably only piece of advice I can give about writing is to always have something to make notes on, whether that's a little notebook, a voice recorder, or a smartphone app. When you get an idea, you write it down. That idea's not going to stick around, and it's not going to come back when it's more convenient for you.
During Camp NaNo some years ago, I was about to go to bed when I thought of something that would solve the current issue with my story. I didn't have anything to write it on, so I willed myself to remember until morning. Well, I can tell you with some certainty that it was a word with about seven letters, and it had a "g" in it. That information did not solve the problem in my story.
Sometimes, I'll have random ideas about revision for NaNo projects I worked on years ago. And you better bet I write those down, because one day, I may actually sit down and fix those stories. If I wait long enough, I might solve all the plot holes with random thoughts.