It's fine to work on any problem, so long as it generates interesting mathematics along the way - even if you don't solve it at the end of the day.

I grew up in Cambridge in England, and my love of mathematics dates from those early childhood days.

Always try the problem that matters most to you.

I tried to fit it in with some previous broad conceptual understanding of some part of mathematics that would clarify the particular problem I was thinking about.

However impenetrable it seems, if you don't try it, then you can never do it.

That particular odyssey is now over. My mind is now at rest.

Some mathematics problems look simple, and you try them for a year or so, and then you try them for a hundred years, and it turns out that they're extremely hard to solve. There's no reason why these problems shouldn't be easy, and yet they turn out to be extremely intricate. Fermat's Last Theorem is the most beautiful example of this.