I found the following inspiring Agnes Martin quote on another blog this morning, which was excerpted from her book of prose, Writings:
"We have been very strenuously conditioned against solitude. To be alone is considered to be a grievous and dangerous condition. So I beg you to recall in detail any times when you were alone and discover your exact response at those times. I suggest to artists that you take every opportunity of being alone, that you give up having pets and unnecessary companions. You will find the fear that we have been taught is not just one fear but many fears. When you discover what they are they will be overcome. Most people have never been alone enough to feel these fears. But even without the experience of them they dread them. I suggest that people who like to be alone, who walk alone will perhaps be serious workers in the art field."
More on Agnes Martin and her work here.