The gospel of Christ is all about joy.
All God's children, except for those very few who in full knowledge openly reject Him, who "deny that the sun is shining at noon-day," as it were, have a place in His heaven. Those who have developed their talents and Christ-like qualities, will qualify for greater responsibilities, and the blessings that go with them. We give those levels of progression the titles of "terrestial" and "celestial" -- and are reminded of the teaching of Christ that within His Father's house are many mansions.
But the point is, for the majority of God's children, we have reason to rejoice.
We will never be perfect in this life. Is that reason to hang our heads, and grovel in the dirt of depression? No! To do that is, verily, to reject Christ and deny His Atonement. Do not make that mistake!
The gospel is Joy, Joy, Joy!