Spoiler alert: it's impossible. If your goal is to eliminate anxiety or "block out" the bad thoughts, whether they are distracting or negative in nature, you're playing a losing game. This can be hard to accept for many athletes...
How you think and talk to yourself is linked to how you feel and act. This may sound obvious, but it should be striking, then, to realize how much you likely talk to yourself in a way that completely forgets this notion. That's your inner critic poisoning the narrative of your mind.