As with every episode so far, I greatly enjoyed listening to a recent episode of the Hurry Slowly podcast, this time with interviewee Bill Duggan. He had some great words of wisdom to share, including:

If we’re talking about the creative side, you certainly can’t force it, and a very simple thing is you can’t solve every problem in one day. You can’t solve every problem in one week. You can’t solve every problem in one year. Some problems you just can’t solve, and you don’t know you can’t solve it until you give up trying to solve it.
He makes the point during the episode that if you know what you're doing, and have done something similar before, then there's no problem in pushing on until midnight to get stuff done. However, if you're working overtime to try and solve a problem, a lot of research suggests that you'd be better off doing something else to allow your subconscious to work on it, and spark those 'aha!' moments.

Source: Hurry Slowly