Why do psychologists, gurus, psychiatrists, etc., always recommend that you do things for others?
Because they understand human nature. Because they know all our pains and hurts and ills make us focus on ourselves, and that when we pay all that attention to our own problems, the problems grow bigger and we grow more self-absorbed, and my world is about the arthritis pain in my right knee (it actually was hurting for a few minutes this morning until I got off my butt and took a very active kid to the park).
Being useful to others makes us realize we are important in the world, and that we are not alone. It can heal us.
Getting absorbed is something can create a level of dissociation that makes us less aware, or even unaware of the pain.
Helping others usually requires some planning, some focus, some activity. Being in motion, looking forward, thinking forward is much less compatible with moldering in depression, slumped in front of a TV or in silence, shutting out the world around us.
For starters.