Writers: how to keep going!

Here's the thing, how do writers keep going? Solidly working away on something  that may never see the light of day and most likely be returned with a terse thank you but no note from agent or publisher. Here's some ideas:
- change your thoughts, ie not 'Why am I doing this?' but  'I choose to write because I enjoy it.' (mostly)
-train yourself not to think about what will happen to your story, just think about writing the best story you can for yourself
-sometimes I surround myself by things I have had published just to remind myself that I can do it
-I have an inspirational picture of a woman holding an old fashioned type writer with the words 'You have to finish it' stuck across it hung just where I can see it if I look up from my computer
- promise myself a trip to the shops/ a browse on ebay/ eat biscuits when you've done your quota.
- sometimes just resign yourself to having a bit of  bad session so plan or do research or go out for a walk
What about you? All ideas greatly received.