A few years ago, I read Albert Einstein's biography written by Walter Isaacson. There was something about Einstein that fascinated me so much, apart from his giant and effective way of thinking, which I have been trying to imitate.
You have this thing of interest, you begin to think about it (curiosities and imaginations), but for him, it took the whole time, the whole days, many years, always thinking about it. Refining after refining until he gets the understanding he wanted. He was entertaining thoughts for a very long time.
So, in general, what I have learned is like the three-year rule of thinking about something of interest which has brought "aha" to you until you get it well. It is not a matter of tomorrow you get the answer; it is the matter of months and years, and even a lifetime. Just never stop asking questions (be curious) and keep imagining.