A Prayer of St Thomas More

I'm quite taken by a prayer that St Thomas More wrote in his breviary reflecting on the Passion of Our Lord. I've taken a copy of it, and as much as I enjoy reading the Olde type, I'm having some trouble understanding the following line:

'To sett my mynde faste upon The, and not to hange uppon the blaste of mennys mowthis'

Can somebody please help me? I'd rather have it explained than use Google. Does 'mennys' mean 'the many's'? As in, let my mind be upon the Lord, rather than the cares of the masses?

I hope that you are all having a holy and fruitful Lent. It is going rather quickly. Soon it will be time for Tenebrae!

Good reading, like good food, can be an awful temptation! There are so many wonderful books, and one comes to the Third Sunday of Lent and discovers more, and wants to devour more, while being in the middle of three other dishes... Things end up lukewarm and sickly. All that remains is for the flies to come, and it all ends up in the bin! A measured composure is a wonderful grace. May the Lord make us acceptable gifts unto Himself.

Quoniam magnus es tu, et faciens mirabilia; tu es Deus solus.