Explanation

"Travel is a portion of torment”, i.e. part of it. 'Torment' here is the pain resulting from hardship involved in riding, walking and leaving behind one's habitual lifestyle. "It prevents you from sleeping, eating and drinking", i.e. travel hinders one from enjoying the pleasures of life perfectly due to the hardship, toil, suffering from heat and cold, fear, separation from family and friends, and rough living conditions. That is because a traveler is usually worried, does not eat or drink his normal food and drink as in ordinary times, and likewise is the sleep. So, if this is the case, then one should return to comfortable life, to his family and country, so that he could look after his family, discipline them and so on.