At some point in life, we have all experienced closed doors. This could be devastating at first, but sometimes closed doors can open up opportunities that were not available to you before. If you experience rejection when submitting a manuscript, a song, or a piece of artwork, then don't allow that closed door to stop you.
If you are a writer, continue to write. If you have the ability to sing, then continue to do so. If you draw or paint, continue to do so because one day an opportunity will open up for your work to be to be discovered. It is very easy to quit when doors are closed in your face, but it takes tenacity to continue to press forward until the right opportunity opens up for you.