Do you have to quote your own work?

Question

Suppose you wrote an article at some point. Then, you wrote a second article incorporating some parts of the first article written by yourself earlier. Do you have to quote that? Or just totally ignore it even if it is almostly exactly the same. PLEASE ANSWER THIS. I REALLY NEED TO KNOW!

Answer 1

I believe it counts as self-plagiarism if you do not.

Answer 2

I'm working in a publishing company, so my answer is "yes you should..."

Answer 3

Yes, you cite the article you published earlier in the third person (usually). How you do so depends on what style you're using to write.