Practice Like You'll Play

The point of practice is to help you perform better when the lights are on, and the best athletes are constantly looking for ways to make their practice replicate the experience of being in a game. 

For a basketball player, practicing free throws is good.

Even better would be: running wind sprints between each pair of free throws, to recreate the heart-pounding breathing the player is likely to experience after getting fouled late in a close game.

This kind of practice translates to many situations beyond sports.

To prepare for a big presentation, looking over your notes may be helpful.

Even better would be: practicing your presentation without any notes, with a smart phone camera rolling. It gives you a chance to experience the thoughts of shoot, what comes next?  before people are watching. It may be uncomfortable, but you'll learn which parts you're not ready for, real fast.

If it’s time to have a crucial conversation with a colleague, practicing with a mirror might be useful.

Even better would be: do a dry run with a coach or close friend, and ask for their feedback. They’ll probably notice behaviors you don’t realize you’re doing.

This kind of creative practice is usually more difficult, takes more energy, and can be more unpleasant because it exposes your weaknesses. But if your goal is better performance with limited time to prepare, modifying your practice to the mimic a "game" environment can be one of the fastest ways to improve.