The downside of naps is that they can take away just what you described, which is sleep pressure ... If you are struggling with sleep at night, avoid naps during the day ... If you are already having problems either falling asleep, which is what we call sleep-onset insomnia, or you can fall asleep but you can't stay asleep, which is what we call sleep maintenance insomnia, you want to build up as much sleep pressure [and] as much sleepiness as you possibly can during the day.