When we take the Sacrament each week, we know we are renewing our baptismal covenants that we made at the time we were baptized, whether that was when we were 8 years old, or later, when we joined the Church.
When we go to the Temple the first time we receive our own endowment, but each time we go after that, we are being reminded of our temple covenants as we perform the work for our deceased ancestors. We are not renewing them.
We renew EVERY covenant we have made with the Lord, be it baptismal or temple, when we partake of the sacrament each week...which is why it is SO important to attend our church meetings and contemplate this renewal process.
Have you ever wished you could have a "clean slate" like when you were baptized???? Well, you do have one each Sunday as you partake of the Sacrament worthily and with awareness.
Such a simple, yet profound, blessing in our lives!!