Sometimes ... praying really is the only useful thing I do

In recent years I've quite often heard myself say something along the lines of "the only useful thing I do in a day is pray".
I suppose it expresses something quite deep inside me about the transitory nature of anything I might do or contribute to, perhaps it also says something about how spirituality holds things together for me. And on days when I feel that I haven't really prayed it also reminds me to continue with the useful useless activity of prayer.
This evening I've been thinking about the final verse of Psalm 90 in French. In the français courant version I have internalised it ends "donne à nos travaux un résulat durable; oui donne à nos travaux un résultat durable" which would translate into English as something along the lines of "grant that our work may last". The Traduction Oecuménique de la Bible has "consolide pour nous l'oeuvre des nos mains". So then I started looking at the English translations and I was really rather disappointed, nothing I've found there really speaks to my soul in the same way as the French does. The English translations seem to me to be either too opaque and old fashioned:
And let the beauty of the LORD our God be upon us:
and establish thou the work of our hands upon us;
yea, the work of our hands establish thou it. (King James)

Or to be embedded in a concept of religious success which put my theological hackles right up, I really didn't like either of these:
Lord our God, treat us well.
Give us success in what we do;
yes, give us success in what we do. (New Century Version)

And may the Lord our God show us his approval
and make our efforts successful.
Yes, make our efforts successful! (New Living Bible)

Anyway here is the TOB version once more:
Que la tendresse du Seigneur, notre Dieu, repose sur nous tous!
Fais prospérer pour nous l'ouvrage de nos mains!
Oh oui! fais prospérer l'ouvrage de nos mains! (TOB)

And here are two English versions I suppose I can live with but they just don't quite mean the same to me as the French does.
May the favour of the Lord our God rest on us;
establish the work of our hands for us—
yes, establish the work of our hands. (Today's New International Version)

And let the beauty of the LORD our God be upon us,
And establish the work of our hands for us;
Yes, establish the work of our hands. (New King James)

So tomorrow morning I shall go to chapel and we will read the whole of Psalm 90 including this short verse "So teach us to count our days that we may gain a wise heart". Perhaps it is the longing for wisdom of the heart that makes me feel that prayer is the only useful thing I do ...