"I already thought of that. I'm way ahead of you."

Those are common things to say when somebody brings us an idea we've already thought of. But don't do that, even if you were already planning to implement that idea.

What we want to do is keep ideas and innovation coming, and saying "I already thought of that" shuts down innovation.

Instead, just say "thank you very much, that's a great idea, we'll implement that."

You get the win, the person feels great when they see that idea implemented, and they're more likely to bring you great ideas in the future.