Trying to memorize a phone number gives me a headache, but studying mathematics doesn't. I don't think this is a native ability (not entirely), but something you pick up with experience.

The analogy between learning math and "holding something in your mind" might be what Anon_User was trying to criticize with this:

Your intuitive thinking about a problem is productive and usefully structured, wasting little time on being aimlessly puzzled. For example, when answering a question about a high-dimensional space (e.g., whether a certain kind of rotation of a five-dimensional object has a "fixed point" which does not move during the rotation), you do not spend much time straining to visualize those things that do not have obvious analogues in two and three dimensions. (Violating this principle is a huge source of frustration for beginning maths students who don't know that they shouldn't be straining to visualize things for which they don't seem to have the visualizing machinery.)