Talmud Eser Sefirot, Volume 1, p. 37, Item 1: This line is similar to a thin tube through which the Light from the Upper Light of Infinity expands and passes into the worlds, into the place where the void exists.
I recommend visualizing not some geometric forms such as a line and a circle, but a relationship between the two objects. I visualize two properties, the connection of which may be achieved through a circle (without limits) and by means of a line (with limits).
Let’s take, for instance, a relationship between two people. The connection between them may be in the form of circles or straight lines. Therefore, try not to paint these relationships in a geometrical form but rather, visualize them by way of emotion.
Question: What does it mean to relate to the friends by through a circle?
Answer: Whose desire prevails, mine or the friends’? After all, we are talking about desires and restrictions over them, aren’t we? The Light of Abundance is present in and fills everything. It all depends on the desire: to what extent you round and straighten it. Hence, in accordance with this, make a decision about how you relate to the others.
If their desires determine everything for you, then you accept them in such a form as not to judge their actions and deeds, which means that you are filling the circle. With what are you filling it? You are filling it with your attitude. Your attitude can be either through a straight line or a circle.
And if it is really so, it might be that you both turn into two circles or even one, if one lies over the other. The key for now is to keep trying to translate these meanings into feelings.
From the 3rd part of the Daily Kabbalah Lesson 10/15/10, TES