Any athlete will want to be in the best possible condition as it relates to his or her chosen activity. Canine disc can be a demanding sport, and if you want to perform at your best, you should give attention to your ability to throw, sprint, stoop, jump, etc., within a limited time frame. This kind of work may not make you a physical specimen, but it will surely help your stamina, flexibility, speed, and lung capacity, to mention a few. Over the years I've struggled with my weight, but I find I'm still able to perform, no matter how I look, as long as I'm getting good, consistent exercise and nutrition. Also, I find my stomach settles down better when I lay off acidic beverages like coffee and juice.
Water works nicely.
I can't say it enough. I'll not preach to you about overworking your dog, because everyone should know that too much too often is not too good. What I would like to say, though, is that if you don't work with your dog in a consistent manner, he will not be in good shape and will not only perform less than his best but could also have difficulty with nagging injuries or worse. This will often take a few weeks or more depending on the condition of your dog. Then begin practicing the things you and your dog will be doing in your Freeflight routine and Mini-Distance.