Finally, some well known quotes from famous mathematicians that are related to your question:
Roger Penrose mathematical thinking:
"My own way of thinking is to ponder long and, I hope, deeply on problems > and and for a long time ... and I never really let them go."
Roger Penrose
$\mbox{}$ Andrew Wiles explanation of how is his experience working in mathematics.
“Perhaps I could best describe my experience of doing mathematics in terms of entering a dark mansion. You go into the first room and it's dark, completely dark. You stumble around, bumping into the furniture. Gradually, you learn where each piece of furniture is. And finally, after six months or so, you find the light switch and turn it on. Suddenly, it's all illuminated and you can see exactly where you were. Then you enter the next dark room...”
“I carried this problem around in my head basically the whole time. I
would wake up with it first thing in the morning, I would be thinking
about it all day, and I would be thinking about it when I went to
sleep. Without distraction I would have the same thing going round and
round in my mind.”
Andrew Wiles
$\mbox{}$ Alan Turing thought about what is mathematical reasoning, and how intense it is.
“Mathematical reasoning may be regarded rather schematically as the exercise of a combination of two facilities, which we may call
intuition and ingenuity.”
“I have such a stressful job that the only way I can get it out of my
mind is by running hard.”
Alan Turing
$\mbox{}$ John Horton Conway comparison of doing maths with playing games.
You get surreal numbers by playing games. I used to feel guilty in
Cambridge that I spent all day playing games, while I was supposed to
be doing mathematics. Then, when I discovered surreal numbers, I
realized that playing games IS math.
John Horton Conway
And the last quote, the beautifulness of the number by Paul Erdos:
Why are numbers beautiful? It’s like asking why is Beethoven’s Ninth
Symphony beautiful. If you don’t see why, someone can’t tell you. I
know numbers are beautiful. If they aren’t beautiful, nothing is.
Paul Erdos