Holiday season and an onslaught of parties are upon us. Cookies and cheese logs lurk around every corner, making it that much easier to succumb to cravings. When you just can’t resist that slice of pumpkin pie, you can blame it on your brain. Turns out willpower really is a muscle.

A new study published in Psychosomatic Medicine: Journal of Biobehavioral Medicine found that succumbing to cravings results from a brain lapse in the area that controls self-restraint. It’s called the dorsolateral prefrontal cortex and it helps people control their own behavior.

Prior studies have shown that upping activity in this part of the brain can cut cravings for delectable foods. But the new research showed what happened when there was less activity in this area. Not surprisingly, a lack of stimulation in this part of the brain can lead to overindulgence in fatty foods. Translation — that sundae starts to sound even better. Any willpower you had to resist quickly diminishes.

So what can you do to arm yourself against the siren song of sundaes and bolster your dorsolateral prefontal cortex? You should know that willpower isn’t unlimited. The more you withdraw in resisting daily temptations, the less you have — say, on the way home from the gym and fast food is calling to you. The good news is that willpower is a muscle and just like your abs, it can be strengthened and chiseled. And good choices, like getting yourself to spin class in the morning, can lead to more good choices – like picking grilled chicken over fried chicken.

Getting enough sleep can also give you the energy you need to say no. So can limiting alcohol, which decreases inhibitions. Writing down your goals can help you keep your eyes on the prize (and away from the dessert table). And when all else fails, just say no.