You probably already know the answer to this one: Repeat the full simulation until you can go through the Practice Mode in one try.
Practice Mode is intended to be a last-minute refresher for that particular simulation just before you have to use that skill in the real world. If you keep getting stuck on certain questions in the virtual world, you’ll likely get stuck on them in real-life, too.
We all have certain concepts or techniques that we struggle with, and that we require more repetition to master. Return to the simulation and repeat it until it's an "unconscious competence."