If I were absolutely doubt free, then I could be sure. Since I am not, I can only work the best that I can in the ways that will increase my faith, while hoping that God will take care of the rest.
And I can work as best as I can at being good so my life and legacy is not too horrible, yet I don't have to risk some horrendous eternal pain afterlife.
Heaven has never been described in a way that sounded appealing to me. Nothing that was different from this Universe could be interesting. A world with no evil, well then there can't be any discernable good. A world with no competition, risk of failure and change? Then there is no point of doing a darn thing. Just sit around on my arse all day eating grapes.
At least the Koran promises virgins.
No evil. Only various levels of glory and joy.
EDIT: Why not be joyful for someone else who has a greater level of glory and joy than I do?