Going to Mass, Middle English style

This prayer is from the Lay Folks Mass Book.

 Can you guess which prayer it is?

http://upload.wikimedia.org/wikipedia/commons/4/4e/Pontifical_Mass_-_15th_Century_-_Project_Gutenberg_eText_16531.jpg

I know to god ful of myght,
And to his moder, mayde bright,
And to alle his halwes dere,
In many synnes of diuerse manere,
And to the fader gosteley,
That I haw synned largely.
In thought, in speche, in delite,
In worde, in werke, I am to wite,
And worthi I am to blame,
For falsly I haw take goddys name.
There-fore I pray seynte mari
And alle halwes specialy,
And the preste to pray for me,
That god haw merci and pitte
Of mi mysdede that mochel is,
For his manhode and his godnys,
And of me wreche that synful is,
And yew me grace of for-yeuenys.

from The Lay Folks Mass Book; or The Manner of Hearing Mass, With Rubrics and Devotions for the People (London: N. Trübner & Co., for the Early English Text Society, 1879), Text F, l.44-60