Depression is biggest cause of failure for sure! But practically speaking it is easy to say that one should fight depression to make their time productive in order to achieve goals but in reality it is difficult to fight because if we could then that situation won't have effected us to make that sadness into depression.

For sure we must all encourage the depressed people to try to fight against it and look at the wider picture in life and see above that particular situation and depression.
Keep bringing on inspiring subjects!