Throwing out tons of different ideas, especially ideas that might seem slightly off-the-wall can be a great idea to pick out a few really good ideas. Brainstorming helps to open up your thinking so that you aren't stuck in the same old thought patterns.
The brainstorming stage isn't about what is or isn't feasible. Avoid limiting yourself when you're brainstorming. This is the time when all ideas are welcome, no matter how silly or unworkable they sound. If you start limiting yourself during this stage of the thinking game, you aren't going to progress very far.
Avoid saying things to yourself during this phase that will shut down creativity rather than encourage it. Catch yourself anytime you say: "That won't work," "We haven't done it that way before," "We can't solve this problem," "We don't have enough time."
For example: say you get stuck while writing your new story. Instead of obsessing over the next stage of the story, start thinking throwing out ideas for what might happen next, or how the story might progress if there were no boundaries on what you could write (even if you needed to change the ending to make the story possible).