How to be sincerely happy for someone else?

i usually just pretend to be happy for my friends/someone else's success or newfound love or riches, but really i might be jealous or may feel somewhat diminished. i need help with this because i am afraid that it might lead to loss of friends that i dont want to lose. any help would be much appreciated. thanks in advance. JH.How to be sincerely happy for someone else?
I don't know how you can be helped, you need to think about it and know deep down that you will be happy for a friend who has been successful, or has won some money. I think the feeling is within you. I love to see my friends become successful, I always think that they deserve it, maybe you can take that approach.