Physical pain/discomfort and anxiety/stress can turn into a vicious cycle where you can't have one without the other.
I have been practicing mindfulness meditation off and on for the last few years. This form of meditation in general involves a focus on the present experiences as they are (living in the now). It can be a good stress-reducer, mood-booster and some even suggest it has immune-boosting powers as well. It includes various techniques such as walking meditations, breathing meditations, body scans, mindful eating practices and yoga.
I started it as a complimentary treatment for my anxiety. Over time, daily practice contributed to a significant decrease in stress which in turn created a decrease in physical pain and discomfort as well as less of a need for anxiety medication.
While I don't consider it a primary treatment for crohn's, it definitely helps me to mentally decompress when my mind is stressed and too focused on the disease or the cramping and other pains I experience from it. For milder symptoms, my body can sometimes relax a bit more through this practice.
If you are looking for resources, there is a man named Jon Kabat-Zinn who is known for bringing mindfulness meditation mainstream through his mindfulness-based stress reduction techniques. There are various books and recordings of his you can use to learn the practice of mindfulness meditation. I warn you, for his recordings, he can be a bit chatty/distracting...but there are others such as Bob Stahl, Chris Croniak and Elisha Goldstein who have very good mindfulness meditation recordings based off of the teachings of Jon Kabat-Zinn. I like to keep some of the short, 5-15min. meditations on my iPod for my lunch break or travel and will do longer, 45min. practices at home.
I would say the body scan meditations and breathing meditations are the most helpful for me.