My guiding principle, as far as possible, is WIBBOW, which stands for “Would I better off writing?”. You can read a succinct summary of it here: Business for breakfast V1: Ch 8 by Leah Cutter.

As I wrote in an article in 2021:

But what if you’re not in the mood? What if you make a number of false starts? This is where a good warm-up exercise comes in. Many people choose to use a writing prompt. I realised today, however, that my warm-up exercise is to write an article. Which is a bit like saying: rather than do a few stretches before going for a run, I go for a run as a prelude to going on a run.

For example, this afternoon I couldn’t get into writing. Apart from various interruptions, nothing flowed. So I decided to update and tweak an article I’d published a few years ago. That was enough to kick-start my creativity. I did more than merely tweak the article: I embellished it with some of the finest prose I’ve come across. I’ve a good mind to ask myself for a signed copy.

Hence this article, because I thought that other writers might also find the idea of writing an article to get them in the mood for writing an article quite attractive. Unlike using a prompt, it doesn’t feel quite so much like time wasted.

You might like to try it yourself.