but isn't religion supposed to make us happy?
Not to my knowledge.
From the user's perspective, religions is man trying to understand the world and his place in it, and to placate imagined the gods underlying thunder, droughts, and earthquakes.
Then came the priesthood, and made religion into something else, but it wasn't to make people happy. It was to find a way that required almost no effort and no manual labor at all to make a living and receive instant unearned societal respect.
Next, the kings discovered how useful religion was. Some began spreading Christianity using armies - from Constantine to the Crusaders to the Conquistadores.
As I see it, Christianity brings comfort from the insecurities it fosters. Without being told that you might go to hell, or that death as the atheist understands it renders life meaningless and morality impossible, you wouldn't find much of interest or value there. I hold none of those beliefs, and therefore, not surprisingly, Christianity has nothing to offer me. Nor Judaism, nor Islam.
Nor the dharmic religions, which I respect more. But I came to the best ideas I have seen from Buddhism, for example, without consulting Buddhists or Buddhist philosophy.
Secular humanism has been fulfilling for me.
Do you mean into my life? Because it adds nothing. What does religion have to offer a person who is happy and not afraid to be extinguished at death?