I suffer from clinical depression.
I know what things I need to do.
But-in the midst of it-I am unable to self-motivate.
Someone telling me "you should go for a walk today" does nothing.
Someone asking "would you like to go for a walk today" does nothing.
Someone saying, "come on, lets go for a walk today" does something-it triggers a completely different part of my brain and even if I don't want to-I am compelled to "follow the instruction". Which-does do something.
I found the hyperbole and a half write up on depression extremely spot on and would suggest those who haven't suffered from depression to read it several times over.
Also: I wrote a post delineating stages of depression (that do not fall in an order-but can happen at any time in any order) with explanations last year. Maybe it can help with understanding too.
If you have questions or thoughts-feel free to pm me or email me via the blogpost.