油断大敵・悪い風邪  Danger comes when you least expect it. A bad cold:

前回いつかかったかわからない風邪をひきました。南の国から帰った安心感、風邪くらい・・・という体力過信、そして現実の寒さによるものですが、10日ほどを反省しながら寝て過ごしました。

I caught a bad cold. I don’t remember when I had it last time. The bad cold must be due to the security of knowing that I was safely back from the south, too much confidence that I am physically strong not to catch a cold and the actual coldness. I was forced to be in bed about 10 days regretting what needs to be regretted.