We always think we know how another person feels, or think. If a person is happy, just accept that that person is happy and be happy for them. Lets not speculate that that person is actually hiding sadness and loneliness just because that person's life looks like it is not as terrific as what it should be.
Take things for what they are. Take things for what they seem. Not everything is a bed of roses, so learn to live with that. But just take what you see and what you see!
If your own life sucks, then that's just too bad...