Inner peace is the key to world peace. You cannot have world peace with individuals who are boiling from the inside and are ready to explode.
If such people are at the helm of affairs, then not only does the person explode, but the countries and communities also explode.
Real happiness and peace can be found in submitting to the commands of the Creator and the Sustainer of this world. Allah has said in the Quran: “Truly, in remembering God do hearts find rest.” (Quran, 13:28)
The religious sense of inner peace is not about accepting everything that is going on and just being happy; there is more to it.