Born to a poor family in Moscow, I ignored mathematics so I could focus on studying gadgets such as electric motors.
After a failed study of music, I turned to mathematics with great success at the university, leading to a research position at the Mathematics Institute in Moscow.
As a student, I took no notes, but was able to recall all of the lectures....leading to my admonition: "lecture notes does only harm, as it distracts the listener's attention from heeding the subject." (see last note below)
My mathematical focus was topological goups, and I wrote the world-translated treatise...plus, I proved Hilbert's Fifth Problem for abelian groups, a task in itself.
I was known for my ability to write mathematics well...and my reply: "The more carefully a book is written, the thinner it becomes and the more work is spent in writing it."
I suffered from multi-fears...possibly not coping with a new situation, not being able to solve a mathematical problem, or not producing significant work.
These fears led to my switch from topology to research in differential equations and the construction of control devices (back to my gadgetry!).
I should add that all of my accomplishments, my research in mathematics, and my fears need to be interpreted within one additional context....due to a tragic explosion, I was totally blind from age 13 on.
L. S. Pontryagin (1908 - 1988)