Being a writer is fraught with doubt: self-doubt throughout the process of creating; the doubt that surrounds submission and rejection; doubt that you will get an agent and then, when you do, if she/he will be able to sell your work.
Is the antidote for doubt faith or trust or a bit of both? Faith that your writing is part of a greater Plan, that you are sharing in the Divine Creative Impulse. Trust that you have done your best and that your agent will do the same. Taking the risk and putting a part of yourself out there to be accepted, or criticized, or ignored.
And while you wait, just keep on writing.