Ah. Well then I agree, that's funny (er, I mean, if "natsu dakara" is an actual commonly-used phrase... I'm not sure that in English we're frequently caught blaming a situation on it being summer...).
Though even then, it doesn't really match the cover.
I like that DVD. You (hehe) could own it and a person could see it on your shelf and it would look like more of a teen-help type self-motivational video than what it really is...