For me, happiness is derived from contentment while pleasure is
derived from gratification.
Happiness can come from engaging in pleasurable activities but can
also include acts of acceptance and forgiveness.
Following along Kevin's opinion, pleasure can decrease over time with
increased exposure and conditioning. Whereas, happiness is more a
state of being, and level of happiness can be viewed as an absence of
sadness. But happiness is a composite of many different factors
emotional, physical, environmental, etc. Therefore, one's sense of
overall happiness as it relates to the personal, family, society,
organisation, community, is complex and ever-changing.
-siu yuin