A good game designer knows that no idea is perfect and that you should start creating now instead of obsessing over the concept, but what happens when something isn't working out? Where do you go from there? Most of game design is based in iteration & feedback which will tell you when one of your ideas isn't working. But the actionable part is only half the battle. One has to develop emotional intelligence to learn from your own mistakes and improve. And that comes from a lot of practice.