Gladly.
That one should seek to free oneself from grief is not something I feel I need to explain, so I'll simply skip that one.
For people who experience grief, joy is not only necessary, but always present. (If nothing else, a time when one isn't experiencing grief is joyous.)
However, if one is freed from grief, one has no need for joy. I'll explain. Imagine, if I could wire the part of my brain that causes me to feel happiness to a button (to use a scenario made by a different member of the forum). If I sat and pushed this button all my life, what kind of life is that? It's not right. Happiness should be essentially a coping mechanism, no more.
In being stoic, one can find peace and clarity in logic. The stoics value this.
Whew. Does that help?