As part of the commandment of dwelling in a Sukkah during the holiday of Sukkot, we sleep (when possible) in a Sukkah. The Gemara explains that a small snack is allowed outside the Sukkah, but a brief nap is not, as it may well become deep sleep.
Our sages ask why we do allow a brief nap while a man is wearing Tefillin, and explain that that leniency is only when he naps with his head between his knees, in a position that will not allow his to fall into a deep sleep.
A brief nap is defined at 60 breaths, and the sages note that King David would only sleep this length. Since he had so much official work to do, on top of his family (18 wives) and his artistic work (Psalms), he minimized sleep to maximize his productive time. Jewish law states that during the day we should not sleep more than this.
If you need to nap, fine, but don’t let it drag out. It is vital that you do not let yourself sleep all day, or get involved in distractions that will lead you to lose track of time. Set reminders and alarms so you do not waste time. Get in the habit of reducing your leisure and using your energy for creative work.
in our generation we also have a danger that a “snack” can lead you to consume a lot of calories. In fact, many snack foods are engineered to encourage you to eat more. It is important to set boundaries with your food, by removing habit forming foods from your diet, or by consciously limiting your calories or perhaps the hours you eat each day.
Our sages note that even a nap with Tefillin on is forbidden for a young man, since he may have a seminal emission, which is improper while wearing his Tefillin (which contain verses from the Bible with God’s name). The Gemara points out that this danger is acute when a young man is napping with his wife present: “שֶׁמָּא יָבוֹאוּ לִידֵי הֶרְגֵּל דָּבָר” lest they come to do the thing they are used to.
This is an interesting language, as it implies that a man and wife in bed together are likely accustomed to having intimate relations, so the man will do what comes naturally and forget he is wearing Tefillin.
Just as a man needs to be aware of his habits for sleeping and eating, he should be aware of his intimate habits as well. Some may want to reduce this if it is interfering with other areas of life, others need to consciously create a habit and expectation that when he and his wife have the opportunity they will act on it. While it may seem that creating a habit of having sex makes it less special, this can help overcome the distractions that come between man and woman.