It comes naturally to some; it takes a lot of effort for others. Till about a decade ago, I belonged to the latter camp. I could not be easily happy for somebody else and their success.
When I would hear about someone’s accomplishment, I would immediately draw a comparison with my own life. I would often judge them or somehow try to rationalise my own jealous feelings; or—my favourite—gossip with friends/family who felt the same way. I don’t think I was any more jealous than the average person, but I became progressively aware of it. After working on it for years, today I’m at a place where somebody else's success makes me genuinely happy.
Being happy for others has gotten particularly easy in the past year or two because I have cut out all nonsense from my life, in order to singularly focus on myself. This involved cutting people loose. As somebody who valued human relationships over everything else, this was not an easy thing to do. But doing this has omitted all drama from my life. After embroiling myself in one form or other for most part of my adult life, I am overjoyed to confess that there is no room for drama and toxic people in my life anymore.
When you spend time alone, you escape any and all rat-races. You are forced to focus on things that bring you happiness. You learn to empathise with yourself. Those who cannot be easily happy for others often have one thing playing in their mind incessantly—their own misery; I say this from experience. It is a condition in some cases. And a pitiable one. How sad is it that no matter how many factors of time and space get applied to some people's lives, they continue to feel jealous and miserable?
Life gives us ample opportunities to learn to be happy for others, to think above and beyond ourselves. Not grabbing these is letting go of an easy opportunity to redeem ourselves.
Being genuinely happy for others is the fastest way to build trust in any relationship. You can tell when a friend is genuinely happy for you or when a family member is using your joyous moment to wallow in their own misery through a snarky comment. Not being happy for others will definitely cause others to lose trust in you. The quality of any relationship is only worth the amount of trust it can hold.
Every worldview is unique, every experience different; how you view yourself is how you view others. There is no ‘other’. It is only when you can be happy for yourself, that you can be happy for somebody else.