If you keep putting a negative spin on it you'll never make it. That alone time is a time of self realization and discorery. A time to become your own best friend and company.
When you fast you change yourself chemically and since every function in our body including thoughts is a chemical process fasting is a great time for self reflection since literaly and chemically you'll be able to look at thing form another prespective that is not the place that you ordinarily percive as "I". One of the very neat realizations I had on my 40 dayer was an understanding of why most if not all mayor religions and spiritual teachings encourage some form of fasting.
For me exercise is always the best way to shut down the internal dialog and negative emotions.