Here's a prayer titled "The Mediator" from "The Valley of Vision: A collection of Puritan Prayers & Devotions" edited by Arthur Bennett (pages 72-73):
I have destroyed myself,
my nature is defiled,
the powers of my soul are degraded;
I am vile, miserable, strengthless,
but my hope is in thee.
If ever I am saved it will be by goodness
undeserved and astonishing,
not by mercy alone but by abundant mercy,
not by grace but by exceeding riches of grace;
And such thou hast revealed, promised, exemplified
in thoughts of peace, not of evil.
Thou hast devised means
to rescue me from sin’s perdition,
to restore me to happiness, honour, safety.
I bless thee for the everlasting covenant,
for the appointment of a Mediator.
I rejoice that he failed not, nor was discouraged,
but accomplished the work thou gavest him
and said on the cross, 'It is finished.'
I exult in the thought that
thy justice is satisfied,
thy truth established,
thy law magnified,
and a foundation is laid for my hope.
I look to a present and personal interest
in Christ and say,
Surely he has borne my griefs,
carried my sorrows,
won my peace,
healed my soul.
Justified by his blood I am saved by his life,
Glorying in his cross I bow to his sceptre,
Having his Spirit I possess his mind.
Lord, grant that my religion may not be
occasional and partial,
but universal, influential, effective,
and may I always continue in thy words
as well as thy works,
so that I may reach my end in peace.