A quick and easy way to check to see if you have a pure heart is seeing how readily willing you are to give a compliment to others.
If your first instinct when you see something nice or hear about the success of someone you feel constricted then know you have jealousy in your heart. If you genuinely feel happy for the other person and you feel secure with yourself it will be very easy to happily give a compliment.
If you see traces of jealousy in your heart, train yourself to be content by realizing that everything is portioned with great wisdom. No one is going to take anything away from you that was meant for you. Realize the wisdom in the distribution of wealth, knowledge, beauty, and success.
This will ease your heart, prevent you from eating yourself up and allow you to enjoy the beauty & success of others while feeling secure within.