Imam Ghazali states,

“Know that the key to happiness is the following of the Sunna (itiba‘ l-Sunna) and the imitation of the Apostle of Allah (iqtida’ bi rasul Allah) in all his comings and goings, motions, and rests even in the aspect of his eating, rising, sleeping and speaking. I do not say this only in regard to his practice in the arts of worship (adab l-‘Abadat), for there is no reason for the neglecting of the practices (al-Sunan) which appear therein, rather I say this in all the matters of customs. Thus there results the absolute following (of Muhammad). Allah said, “If you love God, follow me; God will love YOU.” And Allah also said, “Whatever the Prophet gave you, take it, and whatever he forbids you, desist from it.”  It is incumbent upon you to put on full trousers (al-Sarawil) while sitting and to attire yourself with a turban while standing. It is also incumbent upon you that, when you put on your shoes, you begin with the right foot; that you eat with your right hand; that you cut your fingernails beginning with the forefinger of the right hand and ending with the thumb of the right hand; that you begin with the little toe with the right foot and finish with the little toe of the left foot. Thus in all your movements and rests.…  Moreover you must not show levity in regard to these matters and say that these things appertain only to customs and that there is no meaning to follow these.  For if you do this, there will close against you a great door of the doors of happiness.”