Sometimes when I am going down I say, 'Bring it on!'. It is a self-destructive urge for me and also depression is a familiar place I find oddly comforting (as DechanDawa said). Instead, fight it and do all you can do to stop yourself slipping as the reality of severe depression is hell on earth. I know when I am deeply depressed I long for relief and have SI because of this.

Happiness is real too, and you can feel it again, you will feel it again as the depression passes. Sending HUGS.