Solitude is extremely important, especially for calm abiding or shamatha meditation. […] But actually, outer solitude is not as important as inner solitude, since all disturbances come from within. Therefore, it is more difficult to find inner solitude. We create our own crowd of thoughts that jostle our mind. Since they are within us, these distractions are not easily banished. Though difficult to find, inner solitude is the most important thing; outer solitude alone is not enough. Please try to find real solitude.
from the book “Traveling the Path of Compassion: A Commentary on The Thirty-Seven Practices of a Bodhisattva”