placid

(of a body of water) free from disturbance by heavy waves; "a ribbon of sand between the angry sea and the placid bay"; "the quiet waters of a lagoon"; "a lake of tranquil blue water reflecting a tranquil blue sky"; "a smooth channel crossing"; "scar

उस दिन कितने ही चेहरे प्रफुल्लित और सौम्य होंगे,

A placid behaviour is a basic factor of progress.