Depression gives you a direct signal that you aren't moving in the direction your heart tells you to move.
Expression is the opposite of depression.You have to express yourself ,your thoughts and emotions in order to overcome depression and become the greatest version of yourself.You need to move a little bit,everyday closer to your dream.You need to see yourself already achieving what you want.Depression is a great tool you can use to become the greatest version of yourself because you aren't feeling good enough for being where you are now,you want more,and that's exactly the mindset you need to become successful.The moment you change your depression into full expression is the moment you'll become successful.Maybe it won't happen in weeks or months or even years but if you express yourself every single day you will achieve it in the end.
So why is depression good for you?Because it's telling you that you need to grow,expand and don't waste time.