During my time at university studying pure mathematics I had an interesting experience of doing a challenging sheet of combinatorics problems during a vacation. Every day I attempted one question and got stuck on it. Then the next morning I woke up knowing the solution. It was a recurring thing: this happened every day for about 2 weeks until I had solved all the problems.
For me this a big eye opener about the importance of sleep and relaxed thinking to solve challenging problems.
For me this a big eye opener about the importance of sleep and relaxed thinking to solve challenging problems.