SOME GUYS—YOU KNOW the types—will insist that getting bigger, stronger, and more defined basically requires moving into the gym so you never miss a workout. After all, most gyms have showers, healthy snacks, and comfy stretch mats for sleeping. (And don’t think we haven’t considered it.)

But before you take up permanent residency at Camp Workout, we have something to tell you: Take a break every once in a while.

“Rest allows you to reap the benefits of what you have been working for,” says Will Mann, the regional fitness director of O2 Fitness in Charleston, South Carolina. “It allows your body to recover and ‘catch up’ with the necessary stress you have placed on it.”

So when should you take a day off? As with all things in the world of fitness, it comes down to your goals and current situation. Here’s how to schedule your rest to make the most of your training:

To optimize strength development, rest before

A demanding, strength-focused workout puts intense stress on the body—both on the muscles themselves, and on the neuromuscular system that coordinates your movements to produce optimal force. So when your workout program calls for a heavy-duty day, rest the day before to prime your muscles for top performance.

“For strength gains, you want to be as fresh as possible so you’re ready to lift as much weight as you possibly can for your specific rep range,” Mann says.

That said, those muscles also need time to repair themselves and lay down new fibers. So if you hit your strength day especially hard, and if you’re especially sore, it’s fine to take off the day after—or at least make it a comparatively easy workout.

To optimize muscle gains, rest after

You know the drill for gaining size: To stimulate muscle growth, you need to lift with enough intensity to cause micro tears in your muscles, and therefore trigger the repair cycle. But in order to optimize that repair, you have to allow time for recovery.

“I would suggest taking the day after a big workout to focus on recovery and refueling your body, a.k.a., proper nutrition,” Mann says. “However, strength and hypertrophy are not as far off as some people think, so if you’re in an earlier stage of a hypertrophy program and therefore still trying to set your foundation of strength, take the day off before the big workout, too.”

To optimize speed training, rest after

Whether you’re training for a marathon or a mile, you won’t get better at running unless you run. A lot.

That said, a properly designed training plan will call for a variety of intensities in your workouts: long runs, short/fast tempos, speed work, and easy recovery runs. But even if you work some recovery runs into your schedule, you still need to set aside time for total rest. In even the most intense plans, that usually translates to one rest a week, though “one rest day is most needed on average every tenth day to restore glycogen levels and aid in proper repair to build more strength,” says NYC-based master trainer Shaun Zetlin.

That’s not to say you can’t rest more often: It’s good to rest after a long run or after an intense speed workout, such as hill repeats or grueling sprints on the track.

If you’re sick: rest as you need to

The typical rule of thumb is that if your symptoms are from the neck up (as in a head cold), you can hit the gym, though maybe not quite as hard as you intended. If they’re from the neck down (affecting your breathing or your digestion), it’s wise to take a day off. You should also skip your workout if you have a fever, Zetlin says, since it indicates that your body is working hard to fight infection. If that’s the case, then you don’t need to sacrifice your immune system’s strength on the weight bench.

If you’re hungover: rest now, atone later.

You did it to yourself, so does that mean you deserve a punishing workout? It depends.

“There is something to be said for having the mental fortitude to overcome an obstacle, and not letting it defeat or derail you from your course—to push through no matter what,” says Mann. But be honest with yourself about how you feel. “Most injuries happen when people are tired and/or distracted during their workouts,” Zetlin says. So if you and your amigos really hit it off at last night’s fiesta, swap your next rest day with the workout you were supposed to do todayThis workout program can be your atonement.