Qur'an

Taking one's naffs as one's ilaah

Q: My question is about an ayat in a quran that says, "those who take there nuffs as there illah". What does this ayat mean? 

Can it be possible that  a person goes to his wife, and be worshipping his nuffs even though he goes to his wife and has intercourse in a  way allowed in shariah. What if he is behaving like an animal or acts upon his animal qualities. Is this allowed in sharia? I am not married yet but I am afraid to get married because of tasswuf and wazifahs and the effects they have upon me.