You send out your novel with a hope and prayer. One month later or three months later, it's rejected.
Get over it. Make peace with it, and send your baby out again.
Whatever kind of "NO" you get, don't waste a lot of time trying to read something into the message.
In essence, it's a general form letter. That's all.
That big "NO" is a blow, no doubt. I don't keep mind. My personal reaction is: Read it. Pitch it. I have enough paper work saved. I move on to the next agent or editor on my list. At some point and time, someone will say "YES'