If you have integrity, nothing else matters. If you don't have integrity, nothing else matters.-Alan Simpson". Analyze.

Humans strive for happiness. Materialistic elements can bring happiness which is momentary but the happiness to be long lasting there must be conformity between what you think, what you do and what you say. This conformity gives a peace of mind leading to well being.
It’s the integrity which provides conformity between what you think, what you do and what you say. Hence it’s the behavior of integrity which provides way of happiness.
Lack of integrity leads to constant internal battle leading to voice of conscience constantly reminding the deviations. This leads to loss of mental peace and further loss of happiness.
Gandhiji is remembered and respected all over the world because of integrity manifesting in his every behavior and actions. He is referred as epitome of integrity and it is said that his teachings are relevant even in 21st century.
On the other hand politicians in India are generally mocked and disrespected because of lack of integrity in their behavior. They commit themselves to welfare of people but are constantly seen indulging act of corruption and nepotism.
Integrity leads to happiness and lack of integrity leads to deteriorating of mental and physical well being of individuals. Hence it is said that “If you have integrity, nothing else matters. If you don’t have integrity, nothing else matters”.