Because those might affect not only on physical conditions but also on intellectual works.
Especially we have difficulties in judgment, attention and concentration. So we can less care about appropriate actions for usual works and might be easier to make mistakes.
Therefore qualities of business are apt to decline, moreover we must pay attention to right response to unexpected affairs.
In this last weeks of September, most businesspersons in Japan would have busy days due to end of fiscal period, so we should take care of ourselves and keep in good conditions.