This has reinforced something I have begun to suspect only recently, and over time am growing in certainty about - take holidays, take them often and get away from the daily monotony.

I've experienced the same feelings that the OP mentioned, and when he said he hadn't taken a holiday since 2007, alarm bells started ringing.

My bursts of inspiration, motivation and the flow of new ideas almost always comes during my 'time off' where I am completely disengaged from everything.

Not saying this works for everyone, but at least for the OP and myself, this is certainly true.