Write an acceptance letter to rejection. Explore rejection. What are the other time time you have been rejected? Getting it down in writing helps to take the load off of that little slip of paper that comes in the mail, Sorry. Often the fact that your work wasn't chosen for a magazine triggers your whole history of rejections (Joey and the prom of '82, that guy on the beach in junior high). Get all that out now.
Put it in perspective. Where does the rejection of your writing fit in the global constellation of Rejection for you? How big of a deal is it in terms of what's going on in the larger world? This is not a guilt trip, just a reality check.