Confidence is an amazing tool when you have it. Building confidence is so important for every type of shot but people seem to have the most trouble with putting. Confidence is tied in with your attitude and thought process and combined with practice of course. If you think you are going to miss before you putt then you probably will. Try and say something like "I'm going to make this" before you putt instead of "I hope I make this" or "If I make this..." - THERE IS NO IF! The other approach you can use is to clear your mind before a putt which is what I do. I know I know it's not always that easy even though it sounds easy it is incredibly tough for some people to do but for me the focus and confidence just sort of take over, I don't really know how to teach it.
It is extremely important that you are positive but remember being positive is different from being optimistic and you need to be both. There have been plenty of time when I am still laughing and positive and yet am playing the worst round of my life and I 'know' that my play (or luck) will not get better. Don't get too down on yourself after missing a putt or a bad drive instead try to focus on the next shot and make that one as good as you can. Don't get distracted by the score, your opponents or how much you are ahead or behind or how good or bad you are playing, etc. it will only distract you from your next shot and more importantly your next putt.
You've heard it before: develop a putting routine and stick to it and I will even go out on a limb and say pick a putter and stick to that as well. Some of the worst putting in my life has come right after changing or even thinking about changing putters. Anyway you need to develop a putting routine that works for you and that you can do the same way every time. For practice start this at a distance away from the basket where you cannot possibly miss; we're talking five or ten feet away, this will build muscle memory with your putting routine and also tell your mind that every time you putt the disc is going in the basket. After a while you will find that your 'gimme' range has gotten farther and you will get this feeling that you can't miss a putt even when you are 50 feet away and even if you miss you will still have that feeling next time too!
Breathing exercises are key to my putting game and I use the same sort of techniques taught to Marine Snipers. I won't go to into too much detail on what all of that entails but I'll teach you an easy way to relax your muscles and help you make more putts! Take in a couple deep breathes before you putt as you are walking to your disc. Then while you are going through your putting routine take in a deep breathe and hold it until you are ready to putt and then exhale. When your lungs are completely empty, PUTT! This is when your body is at it's most relaxed position and this will help steady your hands and prevent minor release errors.
Alright so some of this stuff is simple to do or start doing and some of the mental stuff is a lot harder to teach, sorry about that I'm not the best at explaining things sometimes. I'm also not a 1000 rated pro so many of you don't care what I say which is fine. I can only say that I have been through some hard disc golf times and turned it around. In fact just a couple of weekends ago I had a disc golf mental breakdown at Seatac during a tournament and some major putting issues that I have now mainly fixed. I also used to be a low double digit handicap Ball Golfer so I have experience with this sort of thing from that as well. So anyway I hope you enjoyed my write up. See you on the course!