Here's a professional article on goal setting:
http://www.archery-interchange.com/f...tml#post232754
And my method:
http://www.archery-interchange.com/f...tml#post198674
Mental training is also covered in many posts so I suggest a search, and also to read some books on the subject (one of my favourites is 'With Winning in Mind: The Mental Management System' by Lanny R. Bassham).
And don't get hung up on the bad distances, you will find this is not uncommon or unlikely, take your averages and work from there.