Answer: starting and finishing
Explanation: starting is a hard part. Once you sit down and get going, inspiration will start to come. It is actually a pretty amazing experience.
That being said, FINISHING can be extremely difficult. I have so many projects that are sitting on my to-do list. Sometimes inspiration doesn't come, and your sitting there with no idea what to do. It is good to get some space from it, but you have to go back someday and finish.
