Married woman should apply sindur/kumkum: Every married woman should apply sindur is a tradition which is followed unquestionably till today. The reason behind this tradition is not just that it enhances the beauty of the bride. Sindur is mixture of turmeric, lime and mercury. These components help to increase blood pressure and sexual drive in an individual. This also explains why widows are restricted from applying it. Mercury also helps in removing stress.
Nails should not be cut at night: Earlier, there were no sophisticated nail clippers. Even the modern times clippers are also sharp. To avoid any injury, nails are asked to cut only during daytime.
No sweeping floor at night: It is bad luck for the household to sweep floors at night. Well, at night-time, there is not sufficient light. So some important stuff might get swept away.
Worship idols and visit temples: We do worship idols. This is because when we medidate, it is easier to focus into a fixed image rather than on many random objects. Thus it helps to concentrate and channelize our energy.