Proofreading is important because if you have made a mistake then you can correct it before it is published.  Proofreading is my least favourite part of writing but it is so important that you do proofread.  If you don't like reading your own writing then you can get one of your friends to proofread for you.  I proofread my friend's (MrsMalfoyGrace) stories for her some times.  Sometimes when you are writing for hours it doesn't make sense entirely but it is easy to fix. 

Everyone makes mistakes when writing so don't feel bad if you have some incorrect grammar or spelling.  If you try your best and make sure the majority of your writing is correct then it should be okay.