The Importance of Grace in the Eucharist

The Eucharist is hugely significant and there's been debates about what that means Through the years, but I mean that it is affecting something significant. We all probably at points lose sight of that when we're at mass we're getting distracted and we don't really recognize the how that's a mercy to be conferring grace in the sacraments. What are some maybe of of the key principles that Aquinas brings to his teaching of the Eucharist that help us receive these realities more fully well?