As translated in A Dazzling Darkness: An Anthology of Western Mysticism (1985) by Patrick Grant 
Context: The most powerful prayer, one wellnigh omnipotent, and the worthiest work of all is the outcome of a quiet mind. The quieter it is the more powerful, the worthier, the deeper, the more telling and more perfect the prayer is. To the quiet mind all things are possible. What is a quiet mind? A quiet mind is one which nothing weighs on, nothing worries, which, free from ties and from all self-seeking, is wholly merged into the will of God and dead to its own.
                                    
“What weighs on the soul is ignorance of one's own will and worry over the absence of a future.”
Related quotes
“I lost 28 pounds in my divorce…because that's what a soul weighs.”
Love is Evol (2009)
“It's the one thing we never quite get over: that we contain our own future.”
“He tried to weigh his soul to see if it was a poet's soul.”
                                        
                                        "A Little Cloud" 
Dubliners (1914) 
Context: He tried to weigh his soul to see if it was a poet's soul. Melancholy was the dominant note of his temperament, he thought, but it was a melancholy tempered by recurrences of faith and resignation and simple joy. If he could give expression to it in a book of poems perhaps men would listen.
                                    
“True ignorance is not the absence of knowledge, but the refusal to acquire it.”
As quoted by Mark Damazer in "In Our Time's Greatest Philosopher Vote" at In Our Time (BBC 4) http://www.bbc.co.uk/radio4/history/inourtime/greatest_philosopher_celeb.shtml
Inner Freedom: A Spiritual Journey for Prison Inmates (2008)