Here is a prayer from Martin Luther (1483 – 1546):

“Behold, Lord, an empty vessel that needs to be filled. My Lord, fill it. I am weak in the faith; strengthen me. I am cold in love; warm me and make me fervent that my love may go out to my neighbor. I do not have a strong and firm faith; at times I doubt and am unable to trust you altogether. O Lord, help me. Strengthen my faith and trust in you.
Amen.”