I write when ideas come up...
Sometimes when talking with friends and offering my opinion, or giving advice, I think to myself "I should write about that!"
Sometimes, I watch the news and have my own thoughts on worldly events. If I feel strong enough about it I'll sit down and write about my thoughts and turn it into an article.
Sometimes when I have an interesting life experience, and learned something from it that I feel can help others, I'll write about it.
Sometimes I write a comment and suddenly realize I wrote so much that I decide to turn it into a Hub instead. So I back up and just post a short comment. Then I take the text I wrote and copy it into MS-Word to complete it as an article to publish as a Hub.
I find there are so many occasions that bring up ideas for articles. It doesn't depend on the day or the place. It happens anytime and anywhere. Under any circumstance.
We just have to remember to write about it. Sometimes I do overlook that I just had an experience that would be useful for a good article.