According to the law of attraction
When you keep thinking about something constantly
you are attracting that thing....
on the other hand
When you feel negative towards others' happiness,
Life will perceive that
you don't want "that thing" (happiness) in your life.
Therefore you are pushing "that thing" away from your life
There are bunches of that kind of person in our society
I feel so sorry for them
and I wish them a great luck, they're gonna need it