To offer God the essence of one's own being.

Dear friend in God,
it does not matter how bad or corrupt you are, if all your sins have been forgiven, individually and generally, according to the teachings of the church. If you feel that you have done everything within your power to confess and receive absolution, then you can begin the exercise. Even if you still think that you are completely evil and disgusting, even if you are convinced that your self is merely a burden, and this feeling has so completely taken hold of you that you hardly know what to do with yourself, you must still do what I tell you:

“Take” God, the good and kind God – just as He is, without any distortion – and apply Him like a bandage to your wounded self – just as it is right now. Or if you prefer, lift your sick self and strive with all your longing and eagerness to touch God, who is so good and kind. Do not try to think and anxiously examine each individual part of your self or any quality that you have received from God, whether healthy or unhealthy, given by grace or nature, divine or human.

Surely your misleading and inquisitive mind will tell you that this exercise is fruitless, and will continually bother you and suggest that you rationally give it all up and instead go do something truly practical and useful. Although your rational mind considers this exercise useless and even unhealthy, and would like to shorten it as much as possible, do not stop it. Tell your critical mind to leave you alone. (…)
The exercise I have recommended to you is very suitable, for nothing that I could perform and nothing that my examining mind could achieve would bring me as close to God as this simple, almost imperceptible experience: to offer God the essence of my own being.

(correspondence, England around 1380, both sender and recipient unknown)