It was the Sabbath day. It was kept holy in a unique way. Remember the Sabbath day to keep it holy. You were to remember the good things the Lord had done for you. This time of reflection brought strength for the next week.
Communion is a time of reflection.
This do in remembrance of me. It s the remembering that brings the answer. Communion looks back to the cross, remembers the work of Jesus and renews our strength. In Isaiah 40, the word renew actually means exchange. They that wait upon the Lord shall exchange their strength.