Everyone feels sad or blue, but if the feelings persist of longer than you should see a professional

2 weeks

Explanation: Sadness or darkmood if persists more that 2 weeks and if it affects day to day life activities and creates difficulty in sleeping or eating orders then it should be taken as a form of depression.

Depression is a major illness in our society these days, feeling sad for a day or two for some reason is justifiable but more than 2 weeks without any obvious reason should be addressed as a mental health issue.

Hence a mental health professional must be seen.