I forgot to say - "Golf Is Not A Game of Perfect" is one of my all time favorite books. I can't say enough good things about it.
Golf Is Not A Game Of Perfect by Bob Rotella and is considered a must read for any serious (disc)golfer. You mentioned the negative thoughts you are having. This book can absolutely help you create a more positive dialog for yourself. Most of the book is common sense, but it shows step by step how to apply the common sense you already have while you are out on the course.
The original disc golf "high" can be more elusive once you have been addicted for a while. It seems harder to get that same rush of excitement, especially if you are playing the same course over and over again. Even though it has been said already:
Take a few days off and let your tolerance wear off. (Maybe read the book cover to cover instead of playing a few rounds.)
Go to a different course. Take a drive and play that only course on your wishlist. Better yet, add more nearby courses to your wishlist and get out and play them too.
Go throw your next 10 rounds 100% Forehand. You said you need to learn to throw forehand, what better time than now? Make the commitment to throw all your drives, approaches and even putts with a forehand - even if it means getting a double bogey or two. How long did it take until you felt comfortable and had control of your backhand throw? 10 forehand only rounds is a place to start.
Then throw 10 rounds with only your putters. It will be tough to resist breaking out your drivers on that long hole, but you will be amazed at what you can learn about your game if you stick with it for a few rounds.
Hope you can find the fun again soon.:thmbup: