Look, don't get tearful about it. It was one competition. There are loads and loads out there if you look for them. Subscribe to MsLexia for a start, or have a look at the website (there is currently a short story competition on there). And literally hundreds of competitions in the back, for short stories, novels, poems, all sorts. So you didn't get anywhere with this novel competition - enter a short story one. If you win one that is well known (like the MsLexia one) or get shortlisted, then an agent is going to take more notice of you.
Secondly, write. Write a lot. Even if you have to later rewrite it all, at least you will be writing and improving. Make yourself write even if you don't want to. Pick a competition, and tell yourself you'll have finished the novel/story by the deadline and then do it. Many, many more books get started than get finished. If you do finish it, and get rejected by agents, self publish, and see how you do from that.
Thirdly, get critiqued by someone who knows what they are doing. Join a writing group or do a course at your local college. Send in stuff to online forums or MsLexia for others to comment on your work. It may be that you are entering the wrong competitions! I was entering those in Writers Forum magazine, getting nowhere and getting, frankly, crap feedback. The judge didn't "get" the nuances and literary references (some of the comments showed breathtaking ignorance). MsLexia critiques told me to aim for literary short story competitions, not stuff like this (where the judge writes for People's Friend) - my stories were completely wrong for this market/competition. There was nothing wrong with them per se, but I was wasting my time with this competition.
Fourthly, accept criticism, and rewrite. You might love writing, but what you are writing might be really awful and utter drivel. A friend of a friend self published on Kindle. Her book was excruciatingly badly written - the punctuation was all over the place, it was littered with grocers' apostrophes, the dialogue was wooden. She sold five copies of her book to friends and family. That has told her something, and she is now going to evening classes to improve her writing. She has no talent for novels, but she enjoys writing, so why shouldn't she continue? She might discover a talent for something like flash fiction or poetry.
Fifthly, I don't have a fifthly, but just maintain some perspective. Be spurred on, write more, write better. Don't go and sit in the corner and eat worms!