Sorry to hear this, it's tough when this happens isn't it? Try to be kind to yourself this week and do something that you enjoy or value.
My process for rejection with papers or journals is the same as unsuccessful job applications or notices. Keep the paper work and article or application, learn from the experience, give myself 24 hours (and no more) to feel a bit down and to regroup. Then look for new opportunities elsewhere, or work on a different paper or application, and plan to go back to the unsuccessful one a bit later.
It's a pretty tough thing to go through the rejection process but what I have learned is that often time, place and luck figure in these things as well. While I learn from feedback and try to take it on board, I try to be discriminating about this and don't necessarily accept every piece of feedback offered without really processing it and seeing whether it feels like it might be 'true' and if it is helpful.