‘Grace’ is similar to the word for ‘thank you’ in certain Romance languages, and in the context of meal-time grace not surprisingly refers to the gifts we have been given (by God in Christianity, but it applies secularly as well – God gives you a beautiful set of shooting stars, or you are ‘given’ them by, say, the universe – this latter sense of being ‘given’ something makes sense in the context of purposes of meal-time grace, as will be seen).
What is the point of saying grace?
1. Habit for creating gratitude. I.e., it is often an instance of, but can also be thought to point to or be used to remind one of (and so is ‘sacramental’, i.e., a sign) abundance in one’s life (and, in the context of Christianity, also the abundance God wants for us).
It seems that focusing on abundance tends to create abundance in humans – not just a sense of abundance by noticing things that are good, but it also creates more of the good – whatever the psychological mechanisms.
Habitual gratitude – focusing on what’s good in one’s life – is probably a net benefit for most people. (Of course, it should be combined with a kind of realism – accurately seeing problems and taking effective action to respond to them.)
2. It can be thought of as a kind of meditation, as is the case with many kinds of prayer – a short period to empty and quiet one’s thoughts, and then recollect them towards, in this case, a feeling of gratitude or abundance.
3. Signals a starting point for a meal as a social group.
This seems to give the meal more significance for a group.
On top of this, for Christians,
4. Opens to God – it can involve listening to and communicating with God, and developing one’s relationship with Him, or so the idea goes.