I.
When my love swears that she is made of truth,
I do believe her, though I know she lies,
That she might think me some untutor'd youth,
Unskilful in the world's false forgeries,
Thus vainly thinking that she thinks me young,
Although I know my years be past the best,
I smiling credit her false-speaking tongue,
Outfacing faults in love with love's ill rest.
But wherefore says my love that she is young?
And wherefore say not I that I am old?
O, love's best habit is a soothing tongue,
And age, in love, loves not to have years told.
Compare to  Sonnet 138 ’s 9th line: 
 But wherefore says she not she is unjust?
The Passionate Pilgrim: 1