The commands of Allah Ta’ala never change. They are perfect and thus there is no room for any improvement. The Sunnat of Nabi (sallallahu alayhi wasallam) is also perfect and never changes. Our Deen is thus one set code of laws with a perfect way of implementation. If we bring our lives in accordance to Deen, then there will be peace, tranquillity, contentment, direction, focus and meaning in our lives.
On the other hand the system and laws of the material world keep on changing. The material world runs on the intelligence of man which is deficient, thus there is always a need to change and to improve on itself. If we allow the material world to govern our lives, then unfortunately there will be restlessness, confusion and instability in our lives. At times we will be bowing down to a certain country, then to some fashion and trend and then suddenly to some new culture and custom. In the process we have lost our life without having made any progress towards our real destination.