Many people, when they aren't occupied with work or school, get bored. Because we resort to lounging around, watching tv, going online. The repetitive choices we make while we are bored themselves can lead to boredom, out of repetition. Having a "boring day" may just mean not coming up with anything different to do, being more inclined to resort to your average habits (i.e. the things you resort to normally when you're not immediately occupied).
Now, does that make sense?