When you follow the guidance from your Lord you feel inner contentment and peace and happiness.
When you are surrounded by your loved ones and everyone is happy, you are happy.
When you feel that you are making a positive difference in other muslims lives, you are happy.
When you manage to do something difficult, and you succeed in it, you are happy.
When you realize that you are the reason why others are happy, you feel content and happy.
When you help someone, you are happy.
When you are surrounded by positive people you are happy.
When your friends and loved ones shares with you beautiful things about Islam, you are happy.
When you feel that today i managed to pray fajr salah on time, you feel happy.
When you have khusho in salah, you are happy.
When you spend your time on people rather than things you are happy.
When other muslims guide you to do something good and abstain from doing something bad, and you manage it, you are happy.
When you read about all the bounties you will achieve in Jannah and hope that you and your loved ones might achieve that one day, you are happy.
When you do dhikr you feel inner contentment and happiness.
When others treat you with respect and you treat yourself with self-respect, you are happy.
When you send peace and blessings on our Prophet Muhhamad (pbuh) you feel contentment and happiness.