Something that is often mentioned as an important source for writers is using your own experience. This is pretty obvious when you think about it, but, if you're not actively trying to find inspiration for writing, your own useful experiences can easily be forgotten.
Recently I was able to turn a negative and unpleasant experience into a useful writing exercise. So the piece of writing will probably never become anything particularly constructive in this example but not only does it allow me to keep up the mentality of writing regularly it also allowed me to vent how I felt about the experience.
The experience in question was the Christmas Food Shop. I probably had the common experience that most people have involving stress, annoyance and a vow to boycott the supermarket you used as a result. Normally I would rant about this experience for several days afterwards to my unfortunate other half however on this occasion I chose to put down how I felt in words.
As a result I have a piece of something to show for the event, a piece of writing I may use extracts from in the future (you never know) and also a complaint that, should I decided to, I can always forward to the company in question and maybe get some nice vouchers as an apology in return (but that would have effect on the said boycott).
Any experience can be used in your writing and even if it does not create something sellable or even publishable it is an effective method of exorcising the event and your emotions. If it is perhaps a difficult event you want to write about however it is important to mention that you ensure you have the support you need around you as you may find this exercise conjures some difficult emotions.
My ranty vent can be found at http://www.complaintletter.org.uk/christmas-food-shoppin/