Mess up in practice. It’s the cheapest place in the world to be wrong.

Practice exists so errors can happen where nothing depends on them, and playing it safe there wastes the entire point. Attempting only what you can already do means you find out about your limits at the worst possible moment. Cost is the whole difference between the two settings. A mistake now costs an awkward minute, and the same mistake later costs the real thing.

Use the next session to try whatever you would not risk when it counts. Fail at it several times on purpose. If you get through a practice with nothing going wrong, you probably did not learn much in it.