Being a writer is hard. No matter how much you love it, the actual writing process is draining. You spend hours every day creating worlds and situations from your head. You do this on top of all your other commitments, pushing back other diversions such as relaxing, having a better social life etc. Then when you finish writing your book, you immediately turn round and start to edit it. Maybe once, but probably several times. Then, you have to let it out into the world.
Whether it's beta readers, feedback from contests like ABNA, or just the rejection slips from agents and publishers: it's hard. You love your project, your book is invested with hopes, dreams and hours of your life. And you put it out there nine ninety nine times out of a hundred to get rejected.
With so much in life, in order to get something fantastic you have to open yourself up to get hurt. And it's hard to get used to, but I suppose we just have to try.