I'm not connecting enough with this project.
I’m afraid I’ve decided to pass.
This is not for me.
We do not feel strongly enough about your project to pursue it further.
I can only take on projects that spark my passion.
If you have been the recipient of anything like this, you are not alone! And in fact, there's a contest designed just for you - the Twitter feed and website www.litrejections.com is holding their first short story contest for fiction with themes about rejection. Oh, irony, how we love thee...find more info here: http://www.litrejections.com/short-story-prize/
And if you don't already follow them on Twitter @LitRejections, you will be glad you did. There is always an inspirational quote or thought for those who persevere!