This is a pretty good list of strategies for overcoming rejection. This post deals more with freelance and non-fiction type writing, but the same strategies can be applied to fiction publishing as well.
This author suggests the publishing cycle can at times be like a “cosmic tennis match.” I couldn’t agree more. I still think the best strategy for dealing with rejection, as I have said several times before, is to stay in the game. If you miss the return, pick up the ball and serve again. One of my Adventures of Iric stories–which I titled “Memories of the South” for the sake of external publication–was rejected five times before finding the right editor! And often times that is all it is, finding the right person to read your story. This particular story proved too introspective and not action-packed enough for standard fantasy publishers, but it was just the thing Eternal Remedy was looking for.
For me, the worst part of rejection is getting form letters. It sucks to not know why the story was kicked back–Was the writing bad? Did the reader not like the style? Or was it just seen as not a good fit for the publication?–all of these reasons leave you with different implications moving forward and are important for future interactions with that publisher. Most editors send form letters now. It has made the whole process that much more difficult, but what are you going to do?
If you need some help dealing with rejection (or preparing for rejection if you are just starting to try to publish), the article linked below is a good place to start.