You might want to include the following points in your letter:
Cleanliness is next to godliness;
It is a physical, moral, or ritual state of freedom from pollutants.
It is related to one's personal and societal hygiene as well as prevention from various diseases.
Making your environment well organized and dirt free is also one of the key highlights of cleanliness.
Better keep yourself clean and bright; you are the window through which you must see the world. - George Bernard Shaw