When you are a writer of music, words... in fact anything... you can get into a rhythm.
Now, there are good writing rhythms and bad ones, and I have fallen to both of them probably equally. The only real difference in them is that it is very easy to fall out of a good one, and very difficult to get out of a bad one. This being said, I have learned a few techniques to prevent bad patterns emerging.
Recently I noticed that every time I sat down to play, my hands always twisted to the guitar to form the same chords, same progressions over and over. Some of this could obviously be my subconscious telling me I haven't written "The Song" with that set form, but a lot of it is part of an unhealthy writing mindset.
There are two good ways of approaching this problem that I have found. Both of them are acts of diversion. One of them is to pick up a different instrument, one that you are unfamiliar with and try and write on that. Or indeed, try and play the instrument you are using (in my case, guitar) in a different way. Play it on your lap for example, or left-handed. Lots of people use effects to make the guitar seem alien, and that's a totally valid option, although it can often create a dependency for the player.
The second way... The Cover... is the way I have opted for this time around. I decided to learn another artist's song by ear, and interpret it in the way I see fit. I have chosen to learn and play "Daniel" by Bat For Lashes. It's a song that I really love, by an artist that really inspires me.
I've used this 'cover' technique several times with different bands, (and on my own) and it has never failed. When you see how something can work differently to how you are used to, It opens your mind to trying new forms.
I shall be working on it over the next week and if it's any good, I'll post up the results.