limr is on the correct path. Human nature pulls us toward predictability, but habit is the enemy of creativity. You need to change things up. I will list some things I am doing or have done over the years. I used to paint daily and these same things apply.
#1 For me, it is getting off my fat rump and getting some exercise. I am not lazy, I am a salesman by trade and do a lot of driving and I also write a fair amount of code so I'm sitting a lot. For me, exercise really gets the creative juices flowing.
#2 Believe it or not, I change the radio station and listen to different types music, this helps a little.
#3 I recently (few months) have been doing John Hedgecoe projects and these things are so different in that I have no idea what to expect. This makes me see things in a whole different view. Probably the single most beneficial thing for me on this list currently.
#4 Learn something new. I once took up learning scrap booking. It came to me on a whim one day as I walked into this arts and craft store to pick up some markers and these lady's were sitting at these long tables working on stuff. They were having a lot of fun so I asked what they were doing? They talked me into joining them every Saturday. I did it for about three months (couldn't take anymore bitching about their husbands). It did two things... made me a better husband and I used the techniques I learned to make my own scrap book plus incorporate it into painting. It took my painting to another level.
#5 Kept a running list of interesting things I see randomly. I still do this to this day. I then refer to the list and research each item on the internet on those boring days looking for something to do. About 10% of those items turn into a project. Example... many years ago (#9 on my list), I noticed pocket protectors so I wrote it down on the list I had just started. Well, I started taking pictures of them and asking the people what was each item for (no internet then). Some thought I was weird but most were proud to go through them. I eventually gathered enough photos and created a series of small paintings (postcards) of them, 42 in all. Doctors, lawyers, engineers, homeless, etc. I then hand wrote a simple greeting on back of them and mailed them to art dealers, family, and friends. The response was incredible. It can be the most mundane object, sometimes, they are the best.
Hope you find something in this that helps you.